IRLF 


\ 


A     I 


LIBRARY 

OF  THE 

UNIVERSITY  OF  CALIFORNIA. 

Class 


CHEMISTRY  FOR  YOUNG  PEOPLE 


\> 

OF   THE 

UNIVERSITY 

OF 


Reproduced  from  "  Young's  Elementary  Principle*  of  flhfmistry,"  by  permiKsinn  of  7).  Appleton  A  Company 
DlMITRI    IVANOVITCII    MfiNDELfiEFF 

B.  Siberia,  Ic834. 


CHEMISTRY 

FOR 

YOUNG   PEOPLE 

By  TUDOR  JENKS 

AUTHOR  OF  "ELECTRICITY  FOR  YOUNG  PEOPLE/' 
"PHOTOGRAPHY  FOR  YOUNG  PEOPLE/'  ETC. 


WITH  SIXTEEN  ILLUSTRATIONS  AND 
TWENTY-SEVEN    DIAGRAMS 


NEW  YORK 

FREDERICK  A.  STOKES  COMPANY 
PUBLISHERS 


COPYRIGHT,  1909,  BY 
FREDERICK   A.  STOKES  COMPANY 


November,  1909 


ACKNOWLEDGMENTS 

We  take  this  opportunity  of  acknowledging  the  courtesy 
of  the  following  publishers  who  have  helped  us  in  connec- 
tion with  the  illustrations  of  this  book : — 

D.  C.  Heath  &  Company  ("  Descriptive  Chemistry/'  by 
Lyman  C.  Newell). 

J.  B.  Lippincott  Company  (Wurtz's  "  Elements  of  Mod- 
ern Chemistry"). 

Charles  E.  Merrill  &  Company  ("Modern  Chemistry/' 
by  F.  N.  Peters). 

D.  Appleton  &  Company  ("  Elementary  Principles  of 
Chemistry,"  by  A.  V.  E.  Young). 

THE  PUBLISHERS. 


205100 


INTRODUCTION 

IN  purpose  this  book,  like  the  two  preceding  vol- 
umes of  the  series,  which  dealt  respectively  with 
electricity  and  photography,  makes  no  attempt  to 
fill  the  place  of  a  text-book,  either  in  its  contents 
or  its  purposes.  It  is  planned  to  give  the  young 
reader  such  a  general  account  of  the  modern  science 
of  chemistry  as  will  prepare  him  to  know  better 
what  place  the  science  holds  in  modern  life,  and 
how  it  is  related  to  other  sciences.  For  this  reason 
it  is  much  more  general  in  its  nature  than  a  school- 
book  can  be.  It  contains  no  complete  account  of 
any  one  of  the  elements,  no  directions  for  perform- 
ing experiments  or  for  laboratory  work.  It  does, 
however,  give  an  account,  first,  of  the  commoner 
elements  and  such  a  discussion  of  them  as  leads 
to  a  knowledge  of  modern  ideas  of  what  matter  is, 
and  of  its  laws — meaning,  of  course,  by  "  laws  " 
those  general  ways  of  action  which  experiments 
have  made  clear.  When  the  reader  has  thus  gained 
some  acquaintance  with  the  facts  upon  which  mod- 
ern chemistry  is  based,  he  is  told  of  the  broad  prin- 
ciples governing  all  chemical  actions,  and  learns 

vii 


viii  INTRODUCTION 

something  of  the  great  philosophers  and  chemists 
from  whom  we  have  learned  to  make  chemistry  a 
science. 

After  this  general  acquaintance  is  secured,  the 
commoner  elements  are  taken  up,  and  the  reader 
is  told  those  more  important  facts  about  each  which 
should  be  known,  even  to  one  who  desires  no  ex- 
pert knowledge  of  their  qualities.  After  obtain- 
ing such  general  knowledge  of  these  elements,  their 
qualities  and  their  uses,  the  reader  is  led  to  enter 
a  little  more  deeply  into  the  greater  principles  that 
enable  us  to  understand  their  action  one  upon  an- 
other, and  to  become  acquainted  with  the  Periodi- 
cal Tables  wherein  the  relations  of  all  elements  to 
one  another  is  shown  to  depend  upon  their  atomic 
weight.  These  relations  include  the  subjects  of 
valence,  of  atomic  heat,  and,  generally,  of  chemical 
action  as  classified  by  modern  chemists. 

To  the  enormous  subject  of  organic  chemistry, 
or  the  chemistry  of  carbon  compounds,  but  one 
chapter  is  given;  but  in  this  are  set  forth  such 
general  laws  and  rules  as  enable  the  reader  to 
comprehend  the  complexity  of  the  subject  and  the 
methods  by  which  chemists  are  able  to  make  new 
compounds  and  to  predict  their  qualities. 


INTRODUCTION  ix 

After  this  general  review  of  the  subject,  there 
follows  a  discussion  of  the  history  of  chemistry 
and  of  its  relation  to  human  progress,  which  con- 
tains, though  in  brief  form,  the  important  facts 
enabling  young  readers  to  know  the  importance 
of  the  part  played  by  modern  scientific  chemistry 
in  practical  life.  Then  follows  a  set  of  tables 
which  give  in  a  complete  way  the  essential  facts  in 
relation  to  all  elements,  thus  completing  those 
tables  which  in  the  earlier  part  of  the  book  are 
confined  to  the  more  familiar  elements. 

It  may  be  stated,  again,  that  the  object  of  the 
volume  is  to  give  the  young  reader  such  an  interest 
in  chemistry  and  such  a  knowledge  of  it  as  will 
show  its  relation  to  other  branches  of  human  knowl- 
edge, and  will  substitute  in  his  mind  definite  and 
clear  ideas  of  its  main  principles  in  simple  form,  in 
the  place  of  vague  and  useless  notions.  It  is  be- 
lieved that  the  reader  will  find  in  these  pages  all  of 
chemistry  that  can  be  readily  grasped  and  remem- 
bered by  any  except  those  special  students  who  will 
necessarily  go  to  technical  books  for  practical  in- 
formation. 

Even  the  skilled  chemist  cannot  perform  exper- 
iments without  constant  reference  to  text-books, 


x  INTRODUCTION 

and  in  all  sciences  to-day  the  student  is  compelled 
almost  at  once  to  acquire  and  to  use  a  larger  or 
smaller  reference  library.  While  technical  books 
abound  for  the  general  reader  who  wishes  merely 
an  intelligent  acquaintance  with  the  main  princi- 
ples of  any  science,  he  is  often  compelled  to  acquire 
this  knowledge  by  dint  of  combining  extracts  from 
perhaps  a  dozen  volumes.  To  such  a  reader  this 
volume  should  prove  valuable. 

TUDOE  JENKS. 


CONTENTS 

CHAPTER  PAGE 

I.  FROM  ALCHEMY  TO  CHEMISTRY  ....  1 

II.  THE  AIR.    OXYGEN,  OZONE.    BURNING  .  15 

III.  NITROGEN   AND    HYDROGEN 35 

IV.  PROPERTIES  OF  MATTER 51 

Y.  THE  ELEMENTS.    THE  LAWS  or  COMBINA- 
TION   69 

VI.  COAL  AND  CARBON 79 

VII.  NATURE  OF  CHEMICAL  COMBINATION     .     .  93 

VIII.  ABOUT   COMMONER  ELEMENTS     ....  107 

IX.  THE  METALLIC  ELEMENTS 129 

X.  METALLIC  ELEMENTS,  CONTINUED     .     .     .  143 

XI.  METALLIC  ELEMENTS,  CONTINUED     ..    .      .  161 

XII.  SOME  OTHER  METALLIC  ELEMENTS  .     .     .  195 

XIII.  CARBON   AND  ITS   STRANGE   COMPOUNDS     .  213 

XIV.  CHEMICAL  ACTION  AND  ENERGY  ....  227 
XV.  CHEMICAL  LAW.    THE  PERIODIC  SYSTEM     .  245 

XVI.  THE  STORY  OF  CHEMISTRY 261 

INDEX  285 


ILLUSTRATIONS 

FULL-PAGE   ILLUSTRATIONS 
Dimitri    Ivanovitch    Mendel6eff Frontispiece 

FACING  PAGE 

John  Dalton 12 

Joseph  Priestley 22 

Daniel  Rutherford 40 

Inflating  Hydrogen  Balloon .  48 

Dinner  Two  and  One  Half  Miles  Underground     ....  84 

Sulphur    Springs 116 

Drilling  Copper  One  Mile  Underground 140 

Loading  Cars  with  Iron  Ore  in  a  Typical  Mine     ....  146 

Open  Pit  Iron  Mining 156 

Stalagmite  Formation  of  Limestone  Found  in  Caves     .     .  204 

Friedrich  Wohler     ....    V 216 

Sir  Humphrey  Davy     .      .     ^    , 236 

Joseph  Louis  Gay-Lussac 264 

Joseph  Black , 268 

Claude  Louis  Berthollet 272 

ILLUSTRATIONS  IN  TEXT 

Priestley's    Pneumatic   Trough 24 

Wood  Arranged  for  Burning  into  Charcoal 29 

Nitrogen   Prepared  by   Passing    Air  over  Copper     ...  36 

Hofmann  Apparatus  for  Electrolysis  of  Water  ....  42 

Snow  Crystals 44 

Condenser   Arranged   for  the   Distillation   of   Water     .     .  46 


ILLUSTRATIONS 

FACING  PAGE 

Fossil   Found   in  a  Coal  Bed 80 

Section  of  Coal  as  Seen  Through  a  Microscope     ....  82 

Apparatus  for  Manufacturing  Coal  Gas     ......  83 

Section  of  Part  of  Earth's  Crust  near  Mauch  Chunk,  Penn., 

Showing  Layers  of  Coal 86 

Diamonds, 88 

Artificial  Diamonds  (Enlarged)  Prepared  by  Moissan     .     .  89 

Moissan's  Electric  Furnace  for  Making  Diamonds     ...  90 

Vertical  Section  of  Moissan's  Electric  Furnace     ....  91 

Extracting  Sulphur   from  Crude  Ore 118 

Apparatus  for  Purifying  Sulphur 119 

Blast  Furnace  Diagram 147 

Apparatus  for  Rolling  Steel 149 

Converter 153 

Magnets 154 

Preparation  of  Ammonia 186 

Apparatus  for  the  Manufacture  of  Nitric  Acid     ....  190 

Manufacture  of  Phosphorus 192 

Apparatus   for   the   Manufacture  of  Sodium  by   the  Elec- 
trolysis of  Sodium  Hydroxide 197 

Lime  Kiln 204 

Acetylene  Flame 220 

Carborundum   Furnace  233 


OF    THE 

UNIVERSITY 

OF 


Chemistry  for  Young   People 

CHAPTER  I 

FROM  ALCHEMY  TO  CHEMISTRY 

THERE  are  certain  of  the  sciences  with  which  we 
all  know  we  are  concerned  daily.  Some  contribute 
so  directly  to  our  amusement,  or  are  so  universally 
taught,  that  it  is  impossible  to  grow  up  in  entire 
ignorance  of  their  principles.  Even  if  we  do  not 
recognize  that  we  are  dealing  with  scientific  facts, 
yet  we  learn  the  facts  as  children,  and  when  we 
come  to  study  the  science  to  which  they  belong, 
find  that  many  of  its  facts  are  already  known  to 
us. 

One  of  these,  for  example,  is  the  science  of 
physics.  Though  the  name  may  sound  strange  to 
a  young  student,  yet  he  very  soon  finds  that  he  is 
acquainted  with  many  of  the  things  taught  him. 
He  has  learned  that  bodies  have  weight,  are  elastic, 
have  cohesion  or  adhesion,  may  be  measured  and 
compared.  In  botany  and  in  zoology  every  child 
has  some  little  training.  He  learns  to  distinguish 


2        FEOM   ALCHEMY    TO    CHEMISTRY 

one  animal  and  one  flower  from  another,  and  when 
he  is  taught  the  science  that  relates  to  them,  he 
finds  he  has  learned  already  a  great  number  of  facts 
to  which  he  can  apply  the  principles  he  acquires. 

With  chemistry  the  case  is  different.  It  is  one 
of  the  latest  of  the  sciences.  Although  it  is  true 
that  chemistry  enters  into  every-day  life,  the 
changes  with  which  it  is  concerned  are  not  such  as 
can  be  easily  made  clear.  In  order  to  comprehend 
them  at  all,  it  is  necessary  that  there  should  be  a 
wide  acquaintance  with  a  number  of  facts  that  are 
not  readily  understood,  and  indeed  are  not  under- 
stood at  all  until  certain  principles  have  been 
learned.  The  evolutionary  philosophers  have 
taught  us  that  children  go  through,  in  a  way,  the 
same  stages  that  mankind  went  through  in  its  gen- 
eral history ;  and  as  mankind  was  for  ages  ignorant 
of  anything  that  can  truly  be  called  the  science  of 
chemistry,  so  boys  and  girls  do  not  find  it  necessary 
to  understand  the  facts  of  chemistry  in  passing 
through  the  stages  of  their  life  that  correspond  to 
the  early  stages  of  the  life  of  mankind.  The  life 
of  children,  until  they  are  well  grown,  does  not 
require  them  to  know  more  than  is  known  to  the 
savage  races.  It  is  at  a  much  later  period  that 


FEOM  ALCHEMY    TO    CHEMISTRY        3 

they  begin  to  put  questions  to  answer  which  re- 
quires them  to  learn  such  general  principles  as 
those  with  which  chemistry  deals. 

For  many  centuries  mankind  was  satisfied  with 
the  general  idea  that  all  forms  of  matter  were  made 
up  of  different  things  put  together,  but  it  was 
only  late  in  the  history  of  mankind  that  the  obser- 
vation of  the  changes  in  substances  led  to  the  asking 
of  questions  that  could  be  answered  only  by  care- 
ful experiment,  and  it  was  still  later  that  it  became 
possible  to  construct  the  apparatus  that  made  the 
experiments  exact.  It  is  only  within  about  three 
hundred  years,  that  is,  since  the  sixteenth  century, 
that  there  can  be  said  to  be  any  science  of  chemis- 
try. Up  to  that  time,  there  existed,  even  among 
the  wise  men,  only  certain  general  notions  that  had 
added  little  to  men's  knowledge  since  the  days  of 
the  early  Egyptians. 

It  is  difficult  to  give  an  account  of  these  early 
beliefs,  especially  because  where  there  was  so  little 
exact  knowledge,  and  where  each  wise  man,  magi- 
cian, or  priest — and  these  three  capacities  were 
often  united  in  one  individual — imagined  for  him- 
self how  substances  existed,  were  made  up,  or  acted 
upon  one  another,  there  could  be  little  agreement, 


4        FEOM   ALCHEMY    TO    CHEMISTRY 

and  their  notions  cannot  be  reduced  into  simple 
statements. 

There  was  a  general  opinion  that  substances 
were  to  be  roughly  classed  under  four  or  five  head- 
ings, that  is,  were  made  up  of  four  or  five  "  ele- 
ments." These  were  said  to  be  earth,  air,  fire, 
water,  and  ether.  Air  meant  to  the  ancients  every 
sort  of  gas  or  gaseous  substance;  fire  was  any  sort 
of  flame  or  heat,  and  as  life  seems  always  accom- 
panied by  heat,  it  came  to  be  looked  upon  as  the 
principle  of  life;  water  included  all  liquids,  some- 
what as  air  included  all  gases ;  earth  was  a  general 
name  given  to  all  mineral  substances,  and,  indeed, 
practically  to  all  solids.  Ether  is  more  difficult  to 
define.  It  seemed  to  include  something  that  was 
more  spiritual  than  air,  and  was  used  to  explain 
what  could  not  otherwise  be  accounted  for.  As 
the  unknown  region  became  smaller,  there  was  less 
and  less  reference  to  the  ether,  and  in  later  times 
the  element,  air,  was  used  much  as  in  earlier  times 
ether  had  been.  Even  to  Shakespeare's  time  we 
shall  see  that  this  general  conception  of  the  four 
elements  prevailed  among  all  save  the  most  learned. 

It  was  impossible  that  even  the  rude  observa- 
tions of  early  times  should  not  show  that  now  and 


FKOM   ALCHEMY   TO    CHEMISTRY        5 

again  one  of  these  elements  seemed  to  be  passing 
into  another ;  for  a  solid  when  exposed  to  fire  would 
first  change  to  a  liquid,  and  then  would  evaporate 
entirely ;  or,  instead  of  evaporating,  would  give  rise 
to  a  gas  that  caught  fire  and  seemed  to  change  to 
flame.  Thus  the  very  crudest  experiments  would 
show  that  the  element  "  earth,"  or  a  solid,  would 
change  into  the  element  "  water,"  that  is,  a  liquid, 
this  into  a  gas  or  "  air,"  which  in  turn  would  go 
back  to  flame. 

From  such  observations  it  was  certain  that  ex- 
perimenters should  be  led  to  the  conclusion  that 
it  was  possible  for  one  of  their  elements  to  take 
on  the  appearance,  or  to  assume  the  qualities,  of 
another.  At  a  time  when  the  imagination  was 
active  and  was  not  controlled  by  facts  (simply  be- 
cause facts  were  so  little  known),  who  can  blame 
the  old  philosophers  for  their  belief  that  the  ele- 
ments were  capable  of  changing  one  into  another, 
and  thereby  becoming  convinced  that  it  was  possi- 
ble to  convert  one  into  another,  almost  at  will,  if 
only  the  right  method  could  be  found? 

From  such  conclusions  came  the  beliefs  of  the 
alchemists,  and  in  them  we  reach  the  beginnings  of 
the  science  of  chemistry. 


6        FKOM    ALCHEMY    TO    CHEMISTRY 

In  this  name,  chemistry,  we  have  still  the  old 
Arabic  word  that  appears  also  in  alchemy.  Al  is, 
of  course,  the  word  for  "  the,"  as  we  see  it  in  the 
name,  Al-Koran,  or  The  Koran ;  so  alchemy  simply 
means  "  the  chemy."  The  origin  of  the  latter  part 
of  the  word  is  more  or  less  obscure.  So  far  as  it 
has  been  traced,  it  seems  to  signify  the  extraction 
of  the  juice  of  plants  for  medical  purposes,  and 
thence  to  have  come  to  mean  the  making  of  drugs, 
and  processes  akin  to  that.  It  therefore  was  early 
applied  to  the  mingling  and  treating  of  natural  sub- 
stances to  produce  changes  in  them.  In  the  course 
of  time,  those  who  were  skilled  in  these  arts  often 
gave  their  efforts  to  the  search  for  the  means  of 
making,  or  extracting,  the  precious  metals,  silver 
and  gold.  Believing  that  it  was  possible  to  change 
one  substance  into  another,  and  not  knowing 
enough  to  limit  the  possibilities  of  extracting  one 
substance  from  another,  the  search  for  an  easy 
means  to  make  gold  and  silver  was  pursued  by 
most  of  those  who  became  skilled  in  laboratory 
work. 

Knowing  how  futile  were  their  efforts,  we  are 
likely  to  think  of  the  old  alchemists  as  engaged  in 
a  fool's  quest.  But  before  the  rise  of  modern  sci- 


FROM   ALCHEMY    TO    CHEMISTRY        7 

ence,  there  was  no  reason  why  the  ancients  should 
consider  the  making  of  gold  and  silver  out  of  other 
cheaper  substances  as  a  dream.  Indeed,  a  few  his- 
torians go  so  far  as  to  admit  that  some  stories 
recounting  the  success  of  alchemists  seem  to  be 
supported  by  excellent  testimony.  But,  at  all 
events,  the  alchemists  who  searched  for  means  to 
make  gold  and  silver,  and  at  the  same  time  for 
means  to  prolong  human  life,  made  experiments 
and  observations,  learned  methods  and  principles, 
that  have  been  invaluable  in  founding  modern  chem- 
istry. The  history  of  these  old  alchemists  is  most 
fascinating,  for,  besides  the  actual  practical  facts 
of  their  experiments  with  all  sorts  of  substances, 
and  their  studies  into  the  laws  of  nature,  there  is 
a  wealth  of  material  relating  to  their  dreams  and 
fancies  connecting  the  practice  of  alchemy  with 
other  arts  and  sciences,  especially  with  astrology 
and  astronomy.  Many  of  the  beliefs  they  held  in 
regard  to  the  connection  between  the  heavenly 
bodies  and  earthly  substances,  have  left  traces  in 
chemical  terms  and,'  in  words  of  daily  use. 

Each  of  the  metals  was  supposed  to  be  mystically 
related  to  one  of  the  planets.  Gold,  as  the  most 
beautiful  and  least  corruptible  of  metals,  was  as- 


8        FKOM   ALCHEMY    TO    CHEMISTKY 

signed  to  the  sun,  the  greatest  object  in  the 
heavens;  silver,  for  many  reasons,  was  linked  with 
the  moon ;  mercury  named  alike  the  planet  and  the 
metal;  the  red  and  warlike  planet  Mars  had  its 
counterpart  in  the  red-rusting  weapon-metal,  iron ; 
and  the  qualities  and  virtues  assigned  by  astrolo- 
gers to  the  planets  were  believed  to  have  their  coun- 
terparts in  the  properties  of  these  metals.  The 
whole  science,  or  art,  of  the  alchemists  has  been 
well  called  "  the  sickly  but  imaginative  infancy 
through  which  modern  chemistry  had  to  pass  before 
it  attained  its  majority,  or  became  a  positive 
science." 

The  ancient  alchemists  could  go  only  a  certain 
distance  in  their  discoveries.  They  were  patient, 
laborious,  inventive,  and  were  excellent  observers. 
They  were  bold  and  imaginative  in  forming  theories 
about  their  work,  but  they  had  not  the  power  of 
bringing  their  theories  to  the  test  of  proof,  for  they 
lacked  the  necessary  apparatus  to  make  their  ex- 
periments exact  and  conclusive.  This  was  one  rea- 
son why  chemistry  came  late  as  a  grown-up  member 
into  the  family  of  sciences.  Astronomy,  for  exam- 
ple, took  on  the  form  of  a  science  much  earlier, 
since  its  facts  required  little  else  than  observation 


FROM   ALCHEMY    TO    CHEMISTEY        9 

and  the  applying  of  reasoning  to  what  was  seen. 
Long  after  astronomy  had  begun  to  be  truly  scien- 
tific, chemistry  was  still  undeveloped,  and  was  ham- 
pered by  a  mass  of  superstitious  or  magical  theories 
that  had  not  yet  been  cleared  away. 

In  the  sixteenth  century  there  came  about  a 
change  in  the  objects  pursued  by  the  alchemists. 
They  had  hitherto  sought  the  "  philosopher's  stone  " 
— a  magic  substance  that  would  convert  baser  met- 
als into  gold ;  the  "  universal  solvent,"  that  would 
dissolve  all  substances ;  or  the  "  elixir  of  life  " — a 
drink  that  would  prolong  life.  But,  abandoning 
these  wild  quests,  they  now  began  to  believe  that 
their  arts  should  be  devoted  to  finding  out  how  to 
prepare  medicines. 

The  general  terms  used  for  the  four  elements 
about  this  time  began  to  be  replaced  by  more  defi- 
nite words.  The  chemists,  or  alchemists,  of  that 
later  day  replaced  the  old  words,  earth,  air,  fire, 
water,  by  what  they  called  the  "  principles,"  salt, 
silver,  and  mercury.  These  were  believed  to  be 
modifications  of  water,  which  was  considered  the 
true  principle  of  all  things,  and  air  was  considered 
a  separate,  somewhat  unearthly  element.  About 
this  period  also  grew  up  the  recognition  that  the 


10      FKOM   ALCHEMY    TO    CHEMISTRY 

liquids  had  two  general  characters,  being  either 
acid  or  alkaline.  It  was  believed  that  the  health 
of  the  body  consisted  in  a  true  balance  of  these 
opposite  qualities. 

Robert  Boyle,  an  Englishman  living  between 
1627  and  1691,  attacked  these  general  notions, 
pointed  out  the  influence  of  heat  in  forming  new 
bodies,  and  suggested  that  all  things  may  consist 
of  one  universal  matter,  portions  of  which  differ 
from  one  another  in  certain  qualities.  This  uni- 
versal matter  he  believed  to  be  capable  of  forming 
new  bodies  by  a  combination  of  its  smaller  particles 
or  portions.  But,  acute  as  Boyle  proved  to  be  in 
pointing  out  the  mistakes  of  others,  it  was  impos- 
sible that  he  could  then  come  much  nearer  to  the 
truth  than  they  had  done. 

Following  Boyle  came  a  number  of  experimenters 
who  put  forth  various  theories  to  account  for  what 
they  had  noticed  in  their  laboratory  work — of  these 
we  give  a  general  account  in  a  later  chapter.  It 
was  not  until  the  beginning  of  the  nineteenth  cen- 
tury that  chemists  were  led  by  the  researches  of 
Dalton  to  what  we  now  believe  to  be  the  right 
theory  of  the  make-up  of  matter,  the  theory  which 
put  chemical  work  upon  a  true  scientific  basis  and 


FROM  ALCHEMY    TO    CHEMISTRY      11 

thereby  led  to  the  rise  of  modern  chemistry.  That 
modern  chemistry  possesses  all  the  truth,  is  not  to 
be  asserted ;  but  that  it  is  practically  true  has  been 
proved  by  the  control  which  chemists  have  acquired 
over  matter.  They  may  not  know  all  the  facts  in 
regard  to  how  substances  are  formed,  but  at  least 
they  know  enough  to  separate  substances  into  their 
elements,  and  even  how  to  make  these  elements 
join  to  make  new  and  before  unknown  substances. 
Discoveries  in  the  future  may  make  this  knowledge 
more  accurate  in  detail,  but  it  can  never  be  entirely 
set  aside.  In  other  words,  modern  chemistry  is 
true  so  far  as  it  goes,  and  proves  itself  by  its  experi- 
ments. The  old  chemistry  contained  some  truth, 
but  there  was  little  truth  in  the  beliefs  held  by  the 
older  chemists  to  explain  what  they  had  observed. 
With  Dalton,  therefore,  modern  chemistry  begins. 
John  Dalton,  born  September  5,  1766,  in  Eng- 
land, was  a  Quaker.  He  taught  school,  lectured  on 
natural  philosophy,  and  became  interested  in  tak- 
ing observations  of  the  weather.  For  this  purpose 
he  made  an  instrument  for  finding  out  how  much 
water  there  was  in  different  falls  of  rain.  But 
Dalton,  not  satisfied  with  measuring  how  much  rain 
fell,  took  to  asking  the  reasons  why.  He  examined 


12      FROM   ALCHEMY    TO    CHEMISTRY 

how  much  water  was  carried  in  the  air  under  differ- 
ent conditions.  Then  he  was  led  to  inquire  how 
the  vapor  of  water  could  possibly  exist  in  the  air 
without  becoming  mixed  in  with  the  gases  that 
make  up  the  air.  This  led  him  to  reason  upon  the 
question  of  the  mixture  of  gases  one  with,  another, 
which  led  him  to  wondering  how  gases  were  made 
up;  for,  of  course,  each  particle  of  any  gas  still 
remained  itself,  even  when  two  or  more  gases  be- 
came mixed  together. 

In  Dalton's  time  it  was  already .  known  that 
water  consisted  of  the  joining  of  two  gases,  hydro- 
gen and  oxygen.  So  the  studious  Quaker  youth, 
when  he  began  his  keen  reasonings,  found  himself 
obliged  to  account  for  the  fact  that  the  vapor  of 
water  could  be  mixed  generally  throughout  the  air, 
could  then  be  deposited  from  the  air,  as  in  the  fall- 
ing of  dew  or  rain;  could  evaporate,  or  be  taken 
up  by  the  air  again,  all  without  losing  its  identity 
as  water.  Yet  it  was  possible  by  chemistry  to  sep- 
arate this  substance,  water,  into  two  gases,  neither 
of  which  was  like  that  from  which  it  was  separated, 
the  liquid  water. 

When  he  had  thought  out  this  problem,  Dalton 


Itrprudnceil  from  "  Young' i  Elementary  Principles  of  Chemistry,"  by  permission  of  I).  Appleton  <t  Company. 

JOHN  D ALTON 
B.  England,  17GG.     D.   1844. 


FKOM  ALCHEMY    TO    CHEMISTRY      13 

saw  that  there  must  be  two  kinds  of  fine  division 
of  matter.  In  one  kind,  although  a  substance  was 
divided  finely  (for  instance  as  into  the  particles  of 
steam,  which  is  the  vapor  of  water),  yet  there  was 
no  loss  of  identity,  each  little,  or  littlest,  portion 
was  as  truly  the  substance  as  the  largest  mass  of 
it  that  could  be  got  together.  But  there  was 
another  kind  of  division;  for  these  finest  portions 
could,  if  the  proper  means  were  used,  be  separated 
into  portions  which  had  entirely  different  proper- 
ties. Then  these  smaller  portions,  no  matter  what 
was  done  to  them,  could  not  be  further  separated. 

By  means  of  this  reasoning,  verified  by  repeated 
experiment,  Dalton  came  at  length  to  believe  that 
he  had  hit  upon  the  secret  of  the  joining  of  various 
substances  into  new  compounds,  and  that  this  dis- 
covery made  it  possible  to  treat  chemistry  as  exact 
knowledge. 

We  do  not  mean  yet  to  explain  how  Dalton  ac- 
counted for  the  making  of  substances  by  chemical 
laws;  that  we  shall  have  to  discuss  in  the  book  it- 
self, and  it  is  enough  here  to  understand  that  with 
Dalton's  discovery,  made  early  in  the  nineteenth 
century,  we  may  consider  chemistry  as  first  taking 


14      FROM   ALCHEMY    TO    CHEMISTEY 

the  right  road,  the  road  that  has  brought  it  to  the 
control  of  fields  of  industry,  of  research,  and  dis- 
covery, greater,  perhaps,  than  those  belonging  to 
any  other  science.  And  now  that  chemistry  is 
truly  a  science,  it  can  be  brought  into  connection 
and  relation  with  other  sciences. 


CHAPTER   II 
THE  AIR.    OXYGEN,  OZONE.    BURNING 

WE  ourselves  cannot  do  better  than  to  begin  our 
knowledge  of  chemistry  with  the  same  substance 
that  led  John  Dalton,  the  Quaker,  to  his  discovery 
of  the  laws  that  underlie  the  science.  As  he  began 
with  thinking  of  the  air  and  the  raindrops,  or 
water,  so  shall  we.  And  though  for  a  while  we 
shall  postpone  the  subject  to  study  something  of  the 
gases  that  compose  the  air  that  surrounds  us, -yet 
it  will  be  only  that  we  may  better  understand  how 
water  is  composed  of  two  gases ;  for  these  two  sub- 
stances, water  and  air,  properly  studied,  will  tell 
us  a  great  many  of  the  main  truths  of  chemistry, 
and  something  of  the  laws  that  have  to  do  with  all 
chemical  combinations  and  with  the  elements  that 
make  them  up,  for  water  and  air  are  each  well 
known  to  be  composed  of  two  gases. 

In  the  case  of  air,  which  we  may  well  take  first 
in  order,  these  gases  are  simply  mixed,  not  united 
into  a  new  substance.  They  are  the  ones  known  to 

15 


*16  OXYGEN,    OZONE 

chemists  as  oxygen  and  nitrogen,  the  names  mean- 
ing respectively  acid-maker  and  nitre-maker.  Ex- 
actly why  animals  and  plants  should  have  been 
created  so  as  to  need  a  constant  supply  of  this 
mixture  of  gases,  lies  not  only  beyond  chemistry, 
but  beyond  all  the  science  we  have  at  present;  for 
like  many  another  "  why,"  this  has  to  do  with  what 
is  known  as  "  metaphysics."  It  may  be  that  crea- 
tures could  exist,  and  possibly  in  other  worlds  do 
exist,  whose  life  is  supported  by  other  gases,  but 
so  far  as  we  can  know  at  present,  it  is  only  by  the 
use  of  this  mixture  of  the  two  gases,  nitrogen  and 
oxygen,  that  every  living  creature  carries  on  the 
growth  and  the  changes  that  make  up  life.  Each 
of  the  gases  has  its  part  to  play.  Oxygen  may  be 
considered  the  most  active  agent  in  nearly  every 
change  that  takes  place,  but  oxygen  alone  is  not 
fitted  to  the  uses  of  life.  It  has  to  be  mixed  with 
something  that  slows  down  its  action,  or  life  would 
soon  cease.  When  we  make  an  air  that  is  slightly 
richer  in  oxygen,  or  go  to  such  places  as  already 
have  an  atmosphere  in  which  the  oxygen  is  slightly 
more  plentiful  (as  in  mountain  regions,  or  among 
certain  plants  that  give  it  off  freely)  we  find  that 
the  processes  of  life  are  hastened.  Jules  Verne 


OXYGEN,    OZONE  17 

has  illustrated  this  in  a  fanciful  story  called  "  Doc- 
tor Ox  " ;  and  the  same  device  of  imagining  people 
to  live  in  an  air  very  richly  supplied  with  oxygen 
has  been  used  upon  the  stage. 

As  has  been  said,  by  excess  of  oxygen  life  is 
hastened.  Many  of  the  changes  that  make  up  liv- 
ing take  place  more  rapidly,  and  there  is  in  the  case 
of  mankind  an  increase  of  vigor,  a  brightening  of 
the  spirits,  with  a  quickening  of  the  pulse,  and  a 
more  rapid  circulation  of  the  blood.  In  the  nor- 
mal air  something  of  the  same  results  may  be 
reached  if  rapid  breathing  brings  more  oxygen  to 
the  lungs  in  a  given  time. 

In  the  case  of  birds,  for  example,  the  breathing 
is  more  rapid,  so  that  the  blood,  by  means  of  the 
lungs,  receives  more  oxygen  than  in  the  case 
of  mankind.  Consequently  their  circulation  is 
quicker,  and  many  of  their  life-processes  are  more 
rapid  and  intense  than  in  our  own  case.  On  the 
other  hand,  among  the  slow-breathing  creatures, 
such  as  the  reptiles,  the  precise  opposite  is  true. 
Certain  animals  live  at  two  rates  of  speed.  The 
animals  that  hibernate,  or  go  into  a  sort  of  retire- 
ment during  the  winter — bats,  bears,  and  wood- 
chucks,  all  being  examples — there  is  a  slowing 


18  OXYGEN,    OZONE 

down  of  life  during  their  period  of  repose.  They 
breathe  very  slowly,  using  but  little  oxygen,  and 
their  lives  go  on  very  much  as  a  banked  fire  is  kept 
up  when  the  drafts  are  shut  off. 

In  fact,  that  is  precisely  what  takes  place,  for 
the  fire  itself  is  nothing  but  an  example  of  the  ef- 
fect of  oxygen  upon  matter.  If  we  open  the  drafts 
of  a  fire  and  allow  the  lighter,  heated  air  to  be 
drawn  through  the  burning  material,  the  oxygen 
in  the  air  makes  the  burning  rapid  and  the  fuel  is 
soon  consumed.  When  the  drafts  are  shut  off,  and 
air  is  supplied  in  limited  quantities,  since  there  is 
little  oxygen,  the  fire  burns  slowly,  and  if  no  oxy- 
gen is  supplied,  will  cease  to  burn  at  all.  We 
shall  learn,  when  we  come  to  study  oxygen  more 
closely,  that  what  we  call  burning  is  known  in 
chemistry  under  a  different  name.  To  burn  is  usu- 
ally simply  to  oxidize,  that  is,  to  supply  the  gas 
oxygen  to  any  substance  that  is  capable  of  combin- 
ing with  it  to  make  new  substances.  When  com- 
binations take  place,  we  call  the  substance  com- 
bustible ;  the  chemists  call  it  oxidizable.  We  shall, 
in  fact,  soon  learn  to  consider  every  process  into 
which  oxygen  enters  as  a  "  burning."  This  will 
include  our  own  breathing,  which  is  nothing  more 


OXYGEN,    OZONE  19 

than  a  slow  burning  of  the  substances  in  the  blood. 
A  few  combinations  of  other  elements  will  also 
"  burn,"  without  oxygen,  but  only  a  few. 
While  it  is  true  that  pure  air  should  contain 

Vi-tv-i''    £i- 

mainly  only  two  gases,  oxygen  and  hydrogen,  as  a 
matter  of  fact,  the  air  to  which  we  are  accustomed 
is  anything  but  pure.  •  It  always  holds  in  it  much 
moisture,  various  mixtures  of  other  gases,  certain 
very  rare  elements  in  small  quantities,  and  also 
many  forms  of  impurities.  The  atmosphere  about 
us  is  really  nothing  but  a  great  airy  ocean,  con- 
sisting, it  is  true,  mainly  of  oxygen  and  nitrogen, 
but  containing  also,  as  the  watery  ocean  does,  an 
almost  innumerable  variety  of  gases  and  substances 
which  are  constantly  entering  into  it  in  greater  or 
less  proportion,  and  then  being  removed,  increased 
or  diminished,  according  to  circumstances. 

One  of  the  most  important  of  these  is  "  watery 
vapor,"  or  water  in  a  finely-divided  state  mixed 
throughout  the  air  and  held  in  suspension  by  it. 
When  we  for  any  reason  wish  to  secure  air  that  is 
perfectly  dry  and  perfectly  pure,  it  is  necessary 
to  filter  it,  just  as  we  filter  liquids,  through  fine 
screens  or  through  cotton,  and  then  to  pass  it 
through  tubes  containing  certain  substances  which 


20  OXYGEN,    OZONE 

have  the  property  of  taking  up  the  moisture  from 
the  air. 

Those  of  you  who  have  made  photographs  and 
used  the  platinum  paper,  have  learned  how  diffi- 
cult it  is  to  keep  the  paper  absolutely  dry.  It  has 
to  be  stored  in  tin  boxes,  and  in  the  box  is  kept  a 
lump  of  a  chemical  substance  (calcium  carbide)  to 
absorb  the  slight  amount  of  vapor  that  from  time 
to  time  must  get  into  the  box.  But  saying  nothing 
at  present  about  its  impurities  and  mixtures,  we 
will  try  to  find  out  what  we  can  in  regard  to  the 
two  gases  themselves  that  mainly  go  to  form  a  pure 
air.  A  full  table  of  the  air's  composition  will  be 
found  in  the  last  chapter. 

Let  us  mention  in  passing  some  recently  discov- 
ered gases  of  which  the  air  contains  portions  in 
minutest  quantities — that  is,  minute  in  comparison 
with  its  own  bulk,  and  yet  enormous  quantities  if 
they  could  be  separated  from  it  and  collected  to- 
gether. From  Smith's  "Inorganic  Chemistry"  we 
take  a  statement  there  quoted  showing  the  elements 
that  compose  our  atmosphere.  In  the  order  of 
their  weights,  we  should  have  the  following  layers 
resting  on  the  earth.  .  .  .  Five  inches  of  water, 
thirteen  feet  of  carbon  dioxide,  a  mile  of  oxygen, 


OXYGEN,    OZONE  21 

four  miles  of  nitrogen.  Besides  these  there  would 
be  thin  layers  of  the  rare  gases,  argon,  helium,  neon, 
krypton,  xenon.  These  gases,  very  recently  discov- 
ered, seem  to  have  no  tendency  to  enter  into  any 
compounds,  and  <so  are  of  little  importance  in 
practical  chemistry.  The  argon  was  first  discov- 
ered, and  then  by  treating  it  with  liquid  air,  and 
heating  it,  the  other  gases  are  one  by  one  caused  to 
escape.  It  was  only  the  power  to  produce  these 
extremely  low  temperatures  that  led  to  the  finding 
of  these  gases. 

OXYGEN 

The  element,  oxygen,  is  probably  the  best  with 
which  to  begin  the  study  of  chemistry.  It  was  dis- 
covered at  an  early  date,  it  is  more  widely  distrib- 
uted and  more  abundant  than  any  other  element, 
and,  especially,  is  found  in  the  two  great  human 
needs,  air  and  water.  Of  the  air  it  forms  about 
one-fifth  in  volume,  and  in  water  it  is  still  more 
abundant,  forming  eight-ninths  by  weight.  Almost 
half  of  the  earth-crust  itself  is  composed  of  oxygen 
compounds,  and  both  vegetable  and  animal  matter 
of  every  kind  contain  oxygen  in  greater  or  less 
degree.  Thus  it  is  not  an  exaggeration  to  declare 


22  OXYGEN,    OZONE 

that  it  is  found  everywhere  and  makes  part  of  all 
substances  with  which  we  ordinarily  have  to  do. 

The  discovery  of  oxygen  was  made  by  the  English 
philosopher,  Dr.  Priestley,  in  1774,  and  by  the  great 
French  chemist,  Lavoisier,  independently.  The 
name  is  Greek,  coming  from  o££?  and  ^ewaw,  meaning 
literally,  "sour-maker,"  or  "acid-maker."  This 
name  was  given  to  it  when  it  was  found  to  enter 
into  many  compounds  that  if  dissolved  in  water 
produced  acids.  The  word  "  acid  "  means  "  sharp," 
and  was  given  to  these  fluids  because  of  their  sour 
taste,  and  also,  perhaps,  in  reference  to  their  activ- 
ity in  attacking  or  dissolving  other  substances. 

An  easy  method  of  obtaining  oxygen  by  itself 
is  that  employed  by  Priestley  in  his  earliest  experi- 
ments. When  mercury,  or  quicksilver,  is  heated, 
not  to  the  boiling  point,  in  contact  with  air,  its 
surface  becomes  covered  with  a  red  scale.  This 
scale  comes  from  the  combining  of  the  oxygen  in 
the  air  with  the  heated  mercury,  and  it  is  called 
oxide  of  mercury.  By  collecting  it  from  the  sur- 
face of  the  mercury,  and  then  heating  it  once  more 
to  a  higher  temperature,  the  mercury  and  oxygen 
separate,  the  first  as  a  metal,  the  oxygen  as  a  gas. 
If  this  second  part  of  the  experiment  is  carried  on 


Reproduced  from  "  Young's  Elementary  Principles  if  Chemistry,"  by  permission  of  1>.  AiffUvton  Jk  Company. 

JOSEPH  PRIESTLEY 
B.  England,  1733.     D.  Pennsylvania,  1804. 


OXYGEN,    OZONE  23 

in  a  glass  retort,  or  glass  vessel,  the  oxygen  rises 
to  the  upper  part  and  may  be  drawn  off  free  from 
the  nitrogen  and  other  gases  that  were  mixed  with 
it  in  the  air.  The  metallic  mercury  forms  in  glob- 
ules, or  a  film,  on  the  cooler  part  of  the  glass  re- 
tort. 

It  is  just  as  well  to  explain  here  how  this  gas  is 
collected  from  the  retort.  The  retort  may  be,  for 
example,  a  vessel  globular  in  shape,  with  a  long 
narrow  tube  projecting  from  the  top.  To  the  end 
of  this  tube  is  attached  another  tube  of  glass  that 
goes  into  a  pan  of  water.  A  jar  is  filled  with  water 
and  then  turned  upside  down,  with  the  mouth  below 
the  surface  of  the  water  in  the  pan.  The  oxygen 
issuing  from  the  end  of  the  glass  tube  rises  into 
the  jar,  and  as  it  gathers,  displaces  the  water. 
When  enough  has  been  collected,  a  flat  piece  of  glass 
is  slid  over  the  mouth  of  the  jar,  which  can 
then  be  lifted  from  the  pan  and  remain  full  of 
oxygen.  .  /. 

This  arrangement  also  was  due  to  Priestley,  and 
is  called  the  "  pneumatic  trough." 

A  similar  experiment  may  be  made  with  other 
metals  than  mercury.  With  some  the  oxygen  has 
little  affinity,  and  from  these  it  will  readily  part 


24 


OXYGEN,    OZONE 


when  heat  is  applied.     These,  of  course,  are  the  best 
for  experiments. 

Another  experiment  separates  the  oxygen  in 
water  from  the  hydrogen.  This  is  done  by  conduct- 
ing electricity  into  a  jar  of  water,  upturned  as  be- 
fore over  a  pan,  and  providing  another  wire  for  the 
outgo  of  the  current.  As  the  current  is  conducted 


From   Wurtz's   "Elements  of  Modern   Chemistry. 
PBIESTLEY'S  PNEUMATIC  THOUGH 

i. 
through  the  water  from  one  pole  to  the  other,  it 

produces  a  separation  of  the  two  gases  that  are 
combined  into  a  liquid.  One  of  these  gases  gathers 
in  bubbles  at  one  pole,  the  other  gas  meanwhile 
gathering  at  the  opposite.  When  enough  gas  is 
collected  to  form  a  fair-sized  bubble,  it  will  rise 
from  the  water.  If,  now,  two  small  tubes  have  been 


OXYGEN,    OZONE  25 

put  over  the  ends  of  the  wires,  each  will  receive 
only  one  kind  of  bubble.  One,  therefore,  will  con- 
tain oxygen,  the  other  hydrogen. 

Neither  of  these  methods  is  the  one  used  for  mak- 
ing oxygen  commercially  in  large  quantities,  but  the 
principle  is  the  same  in  the  commercial  method.  It 
consists  of  heating  compounds  of  oxygen  until  the 
oxygen  is  given  off  as  a  gas.  The  compounds  often 
used  are  potassium  chlorate  and  manganese  dioxide. 
Sometimes  oxygen  is  got  by  forcing  air  through 
a  tube  containing  a  chemical  that  will  absorb  oxy- 
gen. From  this  compound  the  oxygen  is  after- 
wards recovered.  A  very  recent  method  of  obtain- 
ing oxygen  is  to  condense  air  by  cold  and  pressure 
into  a  liquid,  when,  if  this  liquid  be  allowed  to 
evaporate,  the  nitrogen  that  was  in  the  air  escapes 
more  rapidly  than  the  oxygen,  and  the  liquid  left 
behind  is  almost  pure  oxygen. 

When  the  gas  has  been  obtained,  it  will  be  found 
to  have  these  properties:  it  is  colorless,  odorless, 
tasteless;  it  is  slightly  heavier  than  atmospheric 
air.  When  oxygen  is  left  in  contact  with  water, 
the  water  takes  up  some  of  the  oxygen,  just  as  if 
the  gas  were  dissolved  in  the  water. 

This  last  property  is  most  important.    Any  water 


26  OXYGEN,    OZONE 

that  is  kept  in  agitation,  as  the  ocean  by  its  waves, 
or  a  river  by  its  flowing,  is  constantly  taking  up 
oxygen  from  the  air.  The  oxygen  thus  taken  up 
supports  the  life  of  fishes,  and  also  forms  harmless 
compounds  with  all  sorts  of  impurities  in  the  water, 
thus  making  the  water  wholesome  when  drunk. 
Bemember  that  although  the  water  itself  is  by 
weight  eight-ninths  oxygen,  yet  this  oxygen  is  so 
combined  with  the  hydrogen  in  the  water  that  it  is 
of  no  use  to  the  fishes  in  breathing.  Neither*  is 
much  of  it  available  to  combine  with  other  sub- 
stances, for  it  is  not  "  free."  It  is  the  free  oxygen 
added  to  the  water  that  serves  the  fishes  in  breath- 
ing through  their  gills,  and  also  acts  as  a  purifier. 
The  amount  of  oxygen  thus  dissolved  by  water  is 
only  about  one  part  oxygen  to  thirty-three  of  water. 
The  most  striking  property  of  oxygen  is  the 
readiness  with  which  it  combines  with  almost  all 
other  elements.  A  few  exceptions  are  fluorine,  bro- 
mine, and  the  extremely  rare  gases  already  men- 
tioned. This  "combination"  takes  place  in  vari- 
ous ways.  When  exposed  to  the  air  metals  show 
certain  changes  that  result  from  the  action  of  oxy- 
gen upon  them.  In  the  case  of  iron,  this  change  is 
"  rusting."  The  metal,  iron,  combines  with  oxy- 


OXYGEN,    OZONE  27 

gen  to  make  an  "  oxide  of  iron,"  which  is  only  the 
scientific  name  for  rust.  Lead,  zinc,  and  copper, 
show  a  similar  change  to  a  less  degree.  A  rust  is 
formed  on  their  surface,  but  since  this  rust  is  slight, 
and  is  noticed  mainly  by  their  becoming  dull,  we 
usually  speak  of  these  metals  as  being  tarnished 
by  air. 

Phosphorus  combines  with  oxygen  very  readily 
at  ordinary  temperatures.  An  instance  of  this 
property  is  the  lighting  of  a  sulphur  match.  The 
match  consists  of  phosphorus  and  sulphur  covered 
with  a  little  paint.  Scratching  a  match  removes 
the  paint,  and  slightly  warms  and  compresses 
the  chemicals,  the  oxygen  of  the  air  unites  with  the 
phosphorus,  and  the  heat  thereby  produced  sets 
fire  to  the  sulphur,  which  in  turn  inflames  the  stick. 

The  heat  and  light  caused  by  the  action  of  oxy- 
gen is  what  gives  the  brightness  and  warmth  gained 
in  burning  fuel.  If  a  charred  stick  with  the  small- 
est spark  upon  it  be  thrust  into  a  jar  of  oxygen,  it 
burns  fiercely.  Even  an  iron  wire,  when  heated  to 
redness  and  thrust  into  oxygen,  burns  as  if  it  were 
wood,  throwing  off  sparks  as  it  is  consumed. 

Except  for  the  nitrogen  in  the  air,  the  slightest 
spark  would  result  in  a  most  terrific  and  wide- 


28  OXYGEN,    OZONE 

spread  burning  of  all  sorts  of  substances  within 
reach.  The  quick  combining  with  oxygen,  which 
we  call  burning,  is  not  really  different,  except,  in 
rapidity,  from  processes  that  we  know  by  other 
names.  The  decay  of  wood  and  other  substances, 
and  the  rusting  of  metals,  are  just  as  truly  a  burn- 
ing, or  oxidizing,  as  the  actual  flaming  of  a  lighted 
match.  After  the  process  of  combining  with  oxy- 
gen is  finished,  it  is  found  that  there  is  a  change  in 
the  substances  exposed  to  it,  and  the  compounds 
produced  by  this  oxidizing  or  taking  up  of  oxygen 
are  called,  in  chemistry,  oxides.  If  these  com- 
pounds are  heavier  than  air,  they  are  left  as  a  result 
of  combustion ;  if  lighter  than  air,  they  rise,  and  are 
carried  off,  unless  confined.  Thus  in  an  ordinary 
fire  of  coal  and  wood,  the  carbon  (the  element  of 
which  they  largely  consist  and  which  is  seen  nearly 
pure  in  unconsumed  charcoal)  will,  if  plenty  of 
oxygen  is  supplied  to  the  fire,  form  a  gas  known 
as  "carbon  dioxide."  The  prefix  di,  is  simply  a 
Greek  word  for  "  two,"  or  "  double."  The  carbon 
dioxide,  being  lighter  than  air,  is  carried  off.  If  a 
fire  is  burned  without  sufficient  air  to  provide 
plenty  of  oxygen  for  its  combustion,  only  a  part  of 
the  carbon  goes  off  in  gas,  and  the  rest  remains  in 


OXYGEN,    OZONE  29 

charcoal,  or  pure  carbon.  In  the  old  folk-lore 
stories  boys  and  girls  will  remember  how  often 
"charcoal  burners"  are  spoken  of.  These  people 
made  their  living  by  piling  up  wood  into  great 
heaps,  covering  it  closely  with  clay,  turf,  or  similar 
material,  and  then  setting  fire  to  it,  but  shutting 
off  almost  all  the  air.  This  was  a  method  of  sepa- 
rating from  the  carbon  only  such  substances  as 
would  be  easily  consumed,  and  thus  leaving  the  car- 


SECTION  SHOWING  WOOD  ARRANGED  FOR  BURNING  INTO  CHARCOAL 

bon,  or  charcoal,  ready  to  be  used  again  as  fuel. 
The  value  of  the  charcoal  as  fuel  in  old  times  con- 
sisted in  the  fact  that  it  made  a  clear,  bright  fire, 
burning  slowly,  and  without  much  smoke — an  ex- 
cellent cooking-fire,  before  coal  was  known. 

It  has  already  been  said  that  the  oxygen  drawn 
into  the  body  by  the  lungs  is  used  somewhat  in  the 
same  way  as  when  it  is  admitted  to  a  fire.  It  unites 
at  first  with  the  red  corpuscles  in  the  blood,  and  by 


30  OXYGEN,    OZONE 

these  is  carried  throughout  the  whole  body.  It 
burns  up  the  waste  products  of  the  whole  system, 
thereby  creating  warmth  and  also  getting  rid  of 
useless  material.  One  product  of  this  combining 
in  the  body  is  the  same  "  carbon  dioxide "  that 
we  find  in  fire  smoke;  and  as  that  is  allowed  to 
escape  through  the  chimney,  so  the  carbon  dioxide 
is  brought  back  to  the  lungs  and  breathed  out 
again  into  the  air.  Thus  we  inhale  air  rich  in 
oxygen  and  exhale  air  deprived  of  much  oxygen  and 
rich  in  carbon  dioxide.  Kapid  breathing  increases 
the  speed  of  these  processes,  but  if  carried  beyond 
what  is  reasonable,  produces  a  condition  like  that 
of  fever.  Indeed,  fever  seen  in  disease  is  only  a 
condition  wherein  nature  is  trying  to  oxidize  and 
get  rid  of  an  excess  of  waste  material. 

Although  we  have  said  that  most  cases  of  com- 
bustion mean  oxidizing,  it  must  not  be  thought 
that  wherever  heat  and  light  are  produced,  oxygen 
is  at  work.  The  same  effects  may  be  produced 
by  the  action  of  other  chemicals.  Thus,  for  ex- 
ample, the  gas  chlorine  combines  so  actively  with 
hydrogen  gas  that  there  is  a  true  "  burning,"  which 
sometimes  takes  place  so  quickly  as  to  be  like  an 
explosion.  Sodium  "  burns  "  in  chlorine,  and  phos- 


OXYGEN,    OZONE  31 

phorus  also;  nor  are  these  the  only  examples  of 
the  sort.  Ordinarily,  however,  it  is  true  that  ox- 
idizing is  what  we  mean  by  burning. 

OZONE 

There  is  also,  besides  the  ordinary  form  of 
oxygen,  another  form,  in  which  the  oxygen  is,  as 
it  were,  condensed.  It  is  believed  by  chemists  that 
this  form  comes  about  by  a  different  arrangement 
of  the  particles  of  the  gas  by  which  they  are  able 
to  be  brought  nearer  together.  This  second  form 
is  known  as  ozone,  a  name  derived  from  the  fact 
that  it  has  a  striking  odor,  ozo  being  derived  from 
the  Greek  verb  "  to  smell."  As  you  might  guess 
from  the  name,  while  ordinary  oxygen  has  no  odor, 
there  is  a  sharp  and  characteristic  odor  to  the 
ozone.  The  idea  of  chemists  is  that  in  ozone  three 
of  the  smallest  possible  portions  of  oxygen  are 
grouped  closely  together,  whereas  in  the  ordinary 
form,  only  two  of  them  are  grouped.  They  are  led 
to  this  conclusion  for  the  reason  that  when  oxygen 
is  changed  to  ozone,  it  loses  bulk  and  becomes  only 
two-thirds  as  great  in  volume.  In  this  way  a  hun- 
dred parts  of  ozone  can  be  changed,  or  expanded, 
into  a  hundred  and  fifty  parts  of  oxygen.  This 


32  OXYGEN,    OZONE 

expansion  is  brought  about  by  heating  the  ozone  to 
a  high  temperature.  To  change  it  to  ozone  again, 
it  is  treated  by  what  is  known  as  the  silent  dis- 
charge of  electricity — a  discharge  from  a  multitude 
of  points.  While  oxygen  has  no  color,  a  tube  filled 
with  ozone  and  looked  at  against  a  white  light 
shows  a  slightly  bluish  tinge.  All  these  matters 
will  be  better  understood  after  the  reader  has  gone 
over  the  fourth  chapter  of  this  book. 

Both  oxygen  and  ozone  can  be  condensed  to  a 
liquid  form  by  intense  cold.  In  order  to  bring 
this  about,  ozone  must  be  cooled  to  a  temperature 
of  more  than  a  hundred  degrees  below  zero  Centi- 
grade. Oxygen,  to  be  reduced  to  a  liquid,  must  be 
cooled  to  more  than  — 118°  Centigrade,  and  com- 
pressed under  an  enormous  pressure.  Ozone  weighs 
more  than  oxygen,  being  quite  a  little  heavier  than 
air,  while  oxygen  is  only  slightly  heavier.  There 
is  another  difference  between  the  two  forms  of  the 
gas.  While  oxygen  is  not  easily  changed  from  its 
usual  condition,  ozone  is  what  is  known  as  un- 
stable, that  is,  it  tends  to  change  back  into  oxygen 
under  ordinary  conditions. 

There  are  other  reasons  for  knowing  ozone  to 
be  condensed  oxygen  besides  those  given.  While 
oxygen  is  an  active  gas,  ozone,  as  we  would  ex- 


OXYGEN,    OZONE  33 

pect,  is  even  more  active  in  oxidizing  other  sub- 
stances. 

This,  form  of  oxygen  was  first  discovered  by  pass- 
ing electricity  through  a  tube  of  oxygen.  Ozone 
is  now  known  to  be  produced  in  the  air  during  a 
thunderstorm.  The  odor  suggests  that  of  burn- 
ing sulphur.  As  already  said,  its  action  is  like 
that  of  oxygen,  but  more  active  in  tarnishing  metal, 
bleaching  (by  changing  the  composition  of  coloring 
matter)  and  corroding  many  softer  substances.  It 
has  a  use  as  a  disinfectant.  The  air  contains  cqn- 
stantly  a  very  slight  trace  of  ozone,  wjiich  one  au- 
thority states  is  one  part  in  7.00,-ObO.  It  is  most 
abundant  on  t&e  seashore  and  in  the  open  country 
far  from  cities.  A  recent  theory  ascribes  the  for- 
mation of  ozone  in  the  air  to  the  action  of  the 
"  ultra-violet "  rays  of  the  sun  upon  the  oxygen  in 
the  higher  and  exceedingly  rare  portions  of  the 
atmosphere.  These  rays  are  those  most  active  in 
affecting  the  photographic  plate. 

We  shall  find,  in  considering  other  elements,  that 
a  number  of  them  are  like  oxygen  in  appearing  in 
more  than  one  form.  But  that  these  forms  are 
nothing  besides  the  original  element  can  always 
be  shown  by  changing  one  form  of  the  element  back 
into  another  without  trace  of  any  other  substance. 


CHAPTER   III 

f 

NITROGEN  AND  HYDROGEN 

NITROGEN  makes  up  four-fifths  of  the  atmosphere 
in  bulk.  Its  name  was  derived  from  the  fact  that 
it  was  found  in  saltpetre,  another  name  for  which 
is  nitre.  The  gas,  before  it  was  known  to  be  an 
important  part  of  saltpetre,  went  by  the  name 
"  azote,"  a  word  derived  from  the  Greek  and  mean- 
ing that  it  was  a  gas  which  would  not  support  life. 
This  term  is  still  used  in  some  foreign  countries, 
and  also  occurs  in  the  adjective  "  azotized." 

In  the  air  the  nitrogen  and  oxygen  are  not  com- 
bined chemically,  but  are  merely  mixed  together. 
As  there  is  so  much  free  oxygen  in  the  air,  nitrogen 
can  be  readily  obtained  by  any  means  that  will 
separate  oxygen  from  it.  One  way  of  doing  this 
is  to  pass  a  current  of  air  through  a  tube  contain- 
ing red-hot  copper  filings  or  shavings,  these  being 
used  because  they  give  so  much  surface.  When 
hot,  the  copper  combines  readily  with  the  oxygen, 
making  a  copper  oxide.  Since  the  nitrogen  does 

35 


36 


NITROGEN   AND    HYDROGEN 


not  so  -combine,  it  passes  through  the  tube  free 
from  oxygen,  and  so  cannot  be  collected  in  a  suit- 
able vessel. 

When  thus  obtained,  nitrogen  is  found  to  be  a 
colorless,    tasteless,    odorless    gas,   as   is   oxygen, 
and  slightly  lighter  than  air.    It  will  neither  burn 
nor  will  it  support  combustion — that  is,  a  burn- 
ing substance  thrown  into  nitrogen  will,  for  lack 


NITBOGEN,  PBEPAEED  BY  PASSING  AIR  OVER  COPPER 

of  oxygen,  soon  be  extinguished.  If  breathed  by 
animals,  nitrogen  will  cause  death,  not  because  it 
is  a  poison,  but  because  the  lungs  being  filled  with 
it  are  deprived  of  oxygen. 

Its  principal  use  in  nature,  from  our  point  of 
view,  is  its  value  in  protecting  us  from  the  injury 
that  would  be  done  if  the  air  were  oxygen  unmixed 
with  this  harmless  gas. 

The  reasons  why  chemists  assert  that  air,  though 


NITROGEN   AND    HYDROGEN          37 

made  up  of  a  mixture  of  nitrogen  and  oxygen,  is 
yet  not  a  compound  of  these  gases,  are  these:  If 
the  two  gases  are  mixed  in  the  same  proportions 
as  those  contained  in  air,  we  see  none  of  the  usual 
effects  that  come  from  chemical  action.  There  is 
no  heat,  no  change  in  bulk,  and  the  mixture  be- 
comes like  any  ordinary  air.  Secondly,  as  will  be 
seen  later,  when  chemical  compounds  are  made, 
the  quantities  of  the  various  combining  elements 
are  always  in  fixed  proportions,  and  the  elements 
never  combine  except  in  fixed  amounts.  In  the  air, 
the  proportion  of  nitrogen  to  oxygen  is  not  that  in 
which  they  thus  combine.  Third,  in  chemical  com- 
pounds the  proportions  are  always  the  same  in  the 
same  compound,  but  in  air  the  proportion  of  nitro- 

•>  .       •  \         *•   M    » 

gen  to  oxygen  is  not  always  the  same.  Fourtji,  and 
most  convincing,  air  when  shaken  up  with  a  quan- 
tity of  water  in  a  closed  vessel,  loses  some  of  its 
bulk;  then,  if  the  water  containing  this  dissolved 
air  be  put  into  another  vessel,  and  be  heated,  it 
will  expel  this  air,  and  the  air  will  be  found  to  be 
a  mixture  of  nitrogen  and  oxygen  in  new  propor- 
tions. Instead  of  containing  four  times  as  much 
nitrogen  as  oxygen,  it  will  contain  nearly  twice  as 
much  oxygen  as  nitrogen.  This  would  seem  to 


38          NITROGEN   AND    HYDROGEN 

show  that  the  water  has  dissolved  much  of  the 
oxygen  and  very  little  of  the  nitrogen.  But  if 
the  air  had  been  a  chemical  compound,  the  propor- 
tions of  the  two  gases,  when  the  air  was  recovered 
from  the  water,  would  not  have  changed. 

If  it  be  argued  that  the  excess  of  oxygen  may 
have  come  from  the  water,  the  answer  is  that  in 
that  case  the  water  would  have  changed  its  com- 
position, which  is  not  the  case. 

Besides  its  forming  so  large  a  portion  of  the 
air,  the  gas  Occurs  very  commonly  in  the  form 
of  ammonia,  a  compound  containing  one  atom  of 
nitrogen  to  three  of  hydrogen.  Another  form  in 
which  nitrogen  is  found  most  useful  is  in  nitric 
acid.  Nitrogen  may  readily  be  prepared  by  cover- 
ing burning  phosphorus  that  is  floated  in  a  large 
vessel  of  water.  The  burning  of  the  phosphorus 
is  a  combining  of  oxygen  with"  it,  and  this  oxygen 
being  taken  from  the  air  in  the  jar,  leaves  nitrogen, 
more  or  less  pure. 

Nitrogen,  as  has  been  indicated  in  showing  the 
proofs  that  air  is  a  mixture,  is  not  easily  soluble 
in  water.  It  requires  a  hundred  parts  of  water  to 
dissolve,  or  take  up,  about  one  and  a  half  parts 
of  nitrogen.  Although  the  nitrogen  in  the  air  is 


NITROGEN   AND    HYDROGEN          39 

not  taken  up  by  the  system  when  the  air  is  breathed, 
yet  animal  substances  all  contain  nitrogen,  a  proof 
that  they  procure  this  gas  indirectly.  Most  animal- 
foods  contain  compounds  of  nitrogen,  and  it  is 
from  this  source  that  the  nitrogen  in  the  system 
comes.  As  animals  procure  their  nitrogen  com- 
pounds from  food,  so  plants  obtain  nitrogen  com- 
pounds from  the  soil,  and  if  the  soil  be  exhausted 
of  its  nitrogen,  in  order  to  make  it  productive  it 
must  be  fertilized  by  the  addition  of  nitrogen  in 
some  form.  Not  long  ago  it  was  discovered  that 
certain  plants,  such  as  peas,  beans,  and  clover,  are 
able  to  take  nitrogen  directly  from  the  air  by  the 
aid  of  bacteria,  minute  forms  of  life,  found  upon 
their  roots.  These  bacteria  provide  nitrogen  so 
freely  that  their  roots  serve  to  enrich  the  soil,  and 
thus  take  the  place  of  artificial  fertilizer — that  is, 
an  exhausted  soil  can  be  renewed  in  its  nitrogen 
by  growing  a  crop  of  peas,  beans  or  clover,  upon 
it.  Afterwards,  plants  that  need  the  nitrogen  com- 
pounds will  find  them  in  the  soil  so  enriched. 

Nitrogen  was  discovered  in  1772  by  Rutherford, 
a  Scottish  physician,  who  found  that  it  would  ex- 
tinguish a  candle,  and  suffocate  small  animals  con- 
fined within  it.  Then  the  great  French  chemist, 


40  NITKOGEN   AND    HYDKOGEN 

Lavoisier,  showed  what  part  it  played  in  common 
air,  and  he  it  was  who  gave  the  name  "  azote." 

In  the  branch  of  chemistry  known  as  "  organic," 
nitrogen  plays  a  most  important  part,  and  besides 
its  universal  presence  in  animal  flesh,  gives  rise  to 
compounds  of  very  marked  properties — such  as  the 
albumens,  the  aniline  dyes,  the  explosives,  nitro- 
glycerine and  gun-cotton.  In  inorganic  chemistry 
it  gives  us  nitric  acid,  ammonia,  and  "ammo- 
nium " — which  will  be  explained. 

Having  thus  a  slight  acquaintance  with  the  air 
and  the  gases  of  which  it  is  a  mixture,  let  us  now 
take  up  some  study  of  a  chemical  compound — the 
most  familiar  one  and  that  Dalton  studied. 

As  soon  as  we  begin  to  examine  the  character  of 
the  substance,  water,  we  find  that  we  are  dealing 
with  something  that  is  to  be  sharply  distinguished 
in  certain  qualities  from  that  mixture  of  gases 
known  as  air.  Yet  water,  too,  may  likewise  be 
separated  into  two  gases.  But  precisely  in  the  way 
it  was  proved  that  air  is  only  a  mixture,  and  not 
a  compound  (of  oxygen  and  nitrogen),  so  it  maybe 
shown  that  water  is  not  a  mixture  of  two  gases 
(hydrogen  and  oxygen),  but  is  a  true  chemical 
compound  of  them. 


Young's  Elementary  Principle*  of  Chemistru,"  by  permisxinii of  I).  Applet™  .{•  (Jumpany, 

DANIEL   RUTHERFORD 
B.  Edinburgh,  1749.     D.  1819. 


NITROGEN   AND    HYDEOGEN          41 

Yet  water  was  considered,  only  a  little  over  a 
hundred  years  ago,  to  be  an  element  and  not  separa- 
ble into  anything  simpler.  The  discovery  of  the 
true  nature  of  water  came  about  toward  the  end 
of  the  eighteenth  century,  and  there  were  a  number 
of  steps  before  the  nature  of  this  compound  was 
understood.  Thus  Priestley,  the  discoverer  of  oxy- 
gen, noticed  that  when  a  mixture  of  oxygen  and 
hydrogen  gases  was  exploded,  there  was  a  deposit 
of  drops  of  water  upon  the  cool  sides  of  the  tube. 
About  a  year  later,  another  chemist,  Cavendish, 
showed  that  when  two  parts  of  hydrogen  and  one 
part  of  oxygen  were  mixed  and  exploded,  nothing 
was  left  in  the  vessel  where  the  explosion  took 
place,  except  water. 

Two  years  later,  Lavoisier,  after  going  over  the 
previous  experiments  of  others,  clearly  recognized 
and  explained  just  how  the  two  gases,  and  they 
alone,  when  combined  formed  the  compound,  water. 
When  this  had  been  declared,  other  chemists  proved 
and  verified  the  statement.  This  they  did  by  put- 
ting together  carefully  measured  volumes  of  the 
gases,  causing  them  to  unite  so  as  to  form  a  meas- 
ured quantity  of  water,  and  also  by  taking  apart  a 
quantity  of  water  and  securing  from  it  the  same 


42  NITROGEN   AND    HYDROGEN 

proportions  of  hydrogen  and  of  oxygen.  Thus  early 
in  the  nineteenth  century  it  was  finally  proved  that 
water  was  a  chemical  compound  and  always  con- 
tained precisely  two  parts  by 
volume  of  hydrogen,  and  one  of 
oxygen.  By  weight  there  were 
eight  units  of  oxygen  to  one  of 
hydrogen. 

It  is  easy,  nowadays,  to  ver- 
ify these  results.  If  the  gases 
be  mixed  in  a  tubk,  the  passing 
of  an  electric  spark  through  the 
mixed  gases  causes  them  to 
combine,  forming  pure  water. 
And,  on  the  other  hand,  as  has 
been  noted,  the  electric  current 
in  passing  through  water  will 
separate  its  gases  and  collect 

them  at  opposite  poles. 
HOFMANN  APPARATUS        The  t    wMdl    water      j 

FOB  ELECTROLYSIS  OF 
WATEB.  in    chemical    actions    is    almost 

universal.  It  serves  as  a  means 
by  which  the  elements  can  reach  one  another  and 
act  upon  one  another.  The  combination  of  ele- 
ments is  for  the  most  part  brought  about  only  in 


NITKOGEN   AND    HYDKOGEN          43 

two  ways,  either  by  heat  (or  flame)  or  by  moisture. 
When  perfectly  dry,  most  elements  may  be 
brought  into  contact  without  affecting  one  an- 
other in  the  slightest  degree ;  but  by  "  perfectly 
dry "  is  meant  a  dryness  which  can  only  be 
brought  about  by  careful  manipulation;  and  by 
"  contact "  is  not  meant  a  rubbing  together  with 
pressure — for  this  produces  heat,  and  also  may 
promote  combination  in  other  ways.  Ordinarily 
there  is  in  the  atmosphere  and  in  all  substances 
more  or  less  water  or  watery  vapor. 

We  do  not  need  to  be  told  that  the  amount  of 
this  vapor,  or  water,  varies  very  greatly,  not  only 
from  time  to  time,  but  in  different  parts  of  the 
earth.  We  have  every  degree  of  moisture,  from 
the  parched  and  burning  air  of  deserts,  to  the  more 
than  complete  saturation  of  the  air  which  results 
in  the  heaviest  downpours  of  rain.  It  has  been 
calculated  that  the  average  amount  of  water  in  a 
thousand  parts  of  air  may  be  put  at  about  four- 
teen parts.  Besides  the  enormous  quantities  thus 
held  in  the  air,  we  know  from  our  earliest  studies 
in  geography  that  three-fourths  of  the  whole  sur- 
face of  the  globe  are  covered  with  water.  Even 
those  substances  which  we  ordinarily  consider  dry 


44          NITROGEN   AND    HYDROGEN 

consist  often  for  the  most  part  of  water.  Every 
vegetable  growth,  the  animals,  even  the  rocks  them- 
selves, are  filled  with  this  liquid.  The  human  body 
is  about  seven-tenths  water,  and  most  foods  consist 
of  very  large  percentages  of  water,  from  more  than 
nine-tenths  downward.  We  must  not  forget,  when 
summing  up  all  the  amounts  of  water  on  the  globe, 


From   Wurts's   " Elements  of  Modern   Chemistry" 
SNOW  CEYSTALS 

the  enormous  ice-caps  at  the  poles,  the  ice  cover- 
ings of  mountains,  and  their  snowy  summits. 

Thus  the  whole  world  may  be  looked  upon  as 
permeated  and  soaked  in  this  combination  of  these 
gases,  hydrogen  and  oxygen,  and  the  liquid  they 
form  plays  a  multitude  of  useful  parts  in  all  the 
processes  of  nature.  It  will  dissolve  nearly  all 
substances,  and  with  them  in  solution  flows  freely 
from  place  to  place,  carrying  them  with  it.  It  is 
constantly  being  taken  up  into  the  air,  and  as 
continually  sent  back  again  to  the  world  beneath. 


NITROGEN   AND    HYDROGEN          45 

As  it  moves  about  on  the  surface  of  the  earth  it 
acts  both  chemically  and  physically.  Chemically, 
it  changes  the  substances  with  which  it  is  in  con- 
tact, taking  away  some  elements  and  adding  others. 
Physically,  it  changes  the  shapes  and  places  of  sub- 
stances and  their  compounds,  thus  carving  out  the 
surface  of  the  earth  or  in  other  places  building 
it  up,  decomposes  or  forms  rocks,  and  is,  as  it  were, 
the  life-blood  of  the  world,  causing  in  its  surface 
and  in  its  constitution  changes  similar  to  those 
that  the  blood  brings  about  in  animals. 

Water  also  affects  the  substances  with  which  it 
comes  into  contact  by  absorbing  or  giving  out  heat, 
thus  changing  their  temperature.  In  its  own  trans- 
formation from  solid  to  liquid,  from  liquid  to  vapor, 
and  back  again  to  liquid  and  solid,  it  not  only  af- 
fects the  temperature  of  everything  near  it,  but 
also  takes  up  or  parts  with  contained  chemical 
elements,  thus  working  other  changes.  By  means 
of  water,  both  plants  and  animals  are  enabled  to 
take  up  and  make  use  of  the  elements  and  com- 
pounds that  are  dissolved  in  it  or  carried  along  in 

\»-  '- 

its  substance,  and  as  will  be  seen  later  this  "  dis- 
solving "  is  a  process  that  is  far  from  a  simple  one. 

It  is  nearly  impossible  to  conceive  what  our 


46          NITROGEN   AND    HYDROGEN 

world  would  become  without  water,  and  by  this  it 
is  not  meant  that  we  should  imagine  the  world 
deprived  of  the  two  gases  of  which  it  is  composed, 
but  only  of  their  combination  as  water  in  its  ordi- 
nary liquid  or  vapor  form.  Most  substances,  when 


CONDENSEB  ASBANGED   FOE   THE   DISTILLATION   OF   WATEE 

The  condenser  consists  of  an  outer  tube,  AA,  provided  with 
an  inlet  and  an  outlet  for  a  current  of  cold  water,  which  sur- 
rounds the  inner  tube,  BB.  The  vapor  from  the  water  boiling 
in  the  flask,  C,  condenses  in  the  inner  tube,  owing  to  the  de- 
crease in  temperature,  and  drops  off  from  the  lower  end  of  this 
as  the  distillate,  into  the  receiver,  D,  while  the  impurities  re- 
main behind  in  the  flask. 

deprived  of  water,  would  crumble  away  into  a  pow- 
der. There  could  be  neither  animal  nor  vegetable 
life.  A  number  of  chemical  changes  upon  which 
not  only  life,  but  the  existence  of  numberless  com- 
pounds depend,  would  altogether  cease.  Even 
where  much  of  the  water  has  disappeared  from  a 


NITROGEN   AND    HYDROGEN          47 

heavenly  body,  as  in  the  case  of  the  moon,  the 
result  is  to  make  it  a  dead  and  apparently  useless 
body  floating  in  space. 

It  is  unnecessary  to  say  to  any  thoughtful  reader 
that  the  taking  away  of  water  from  the  substances 
at  man's  command,  even  if  he  could  live  without 
it,  would  stop  nearly  every  species  of  human  labor 
— beginning  with  all  agriculture. 

HYDROGEN 

Of  oxygen  we  have  already  told  the  few  most  im- 
portant facts.  But  hydrogen,  the  other  constituent 
of  water,  is  even  more  interesting,  as  will  be  seen 
before  even  this  elementary  book  is  finished.  There 
is  indeed  a  theory  that  all  things  may  be  variations 
of  this  one  element — hydrogen. 

Of  all  substances,  the  element  hydrogen  is  the 
lightest.  Air  is  about  fourteen  and  a  half  times 
as  heavy  as  hydrogen;  oxygen  is  sixteen  times  as 
heavy,  and  water  eleven  thousand  times  as  heavy 
for  the  same  volume.  In  our  atmosphere,  a  mass  of 
hydrogen  floats  rapidly  upward,  as  a  cork  rises 
in  water;  therefore  in  pouring  it  from  one  vessel 
to  another,  it  must  be  poured  upward  instead  of 
downward. 


48          NITKOGEN   AND    HYDEOGEN 

A  very  ready  method  of  showing  the  lightness  of 
hydrogen  as  compared  with  air,  is  to  use  this  gas 
for  inflating  a  small  balloon,  or  even  for  blowing 
soap-bubbles  by  means  of  a  clay  pipe  thrust  into 
a  rubber  tube  connected  with  a  reservoir  of  hydro- 
gen. The  balloon,  or  bubble,  rises  in  the  air  with 
great  rapidity.  Hydrogen  was  formerly  used  for 
inflating  balloons,  but  other  gases,  such  as  illumi- 
nating gas,  are  now  found  to  be  cheaper  and  better 
for  the  purpose. 

When  chemists  decided,  long  ago,  to  arrange  ele- 
ments in  tables  with  a  statement  of  their  relative 
weights,  hydrogen  was  selected  as  the  substance 
by  which  to  measure  the  weight  of  all  other  ele- 
ments. Just  as  in  measuring  lengths  the  metre  or 
the  foot  is  taken  as  the  unit  of  measurement,  so  the 
weight  of  hydrogen  is  called  the  unit.  The  smallest 
possible  amount  of  any  element  is  called  an  "  atom," 
and  this  word  has  long  been  used  to  describe  a  part 
of  it  so  small  that  it  could  be  separated  further. 
Consequently,  a  single  atom  of  hydrogen  is  taken 
to  weigh  "  one  unit  of  weight."  Then  by  measuring 
the  weight  of  any  other  element,  or  substance,  or 
finding  the  number  of  times  it  will  contain  this 
weight,  we  may  get  a  number  that  will  express  its 


i" 

I  I 

•s      < 
«      * 

r 


NITKOGEN   AND    HYDKOGEN          49 

weight  as  compared  with  hydrogen.  In  each  case 
the  amount  considered  is  one  atom.  Since  oxygen, 
for  example,  weighs  sixteen  times  as  much  as  hy- 
drogen, when  equal  volumes  of  the  two  gases  at 
the  same  temperature  and  pressure  are  compared, 
we  may  say  that  the  atom  weight,  or  atomic  weight, 
of  oxygen  is  sixteen,  that  of  hydrogen  being  one. 

A  little  thought  will  show  the  reader  that  this  is 
as  near  as  we  can  get  to  stating  the  weight  of  any- 
thing. We  must  always  compare  a  substance  with 
some  standard  and  state  that  it  is  heavier  or  lighter, 
and  so  much  heavier  or  so  much  lighter,  than  the 
chosen  standard.  There  is  no  other  way  of  telling 
what  weight  is.  From  this  it  follows  that  there  is 
no  answer  to  the  question,  What  does  the  "  1  unit  " 
mean  when  taken  as  the  weight  of  a  hydrogen 
atom?  We  can  only  say  that  it  means  the  weight 
of  an  atom  of  hydrogen — or  if  the  weight  of  any 
other  atom  be  taken  as  standard,  then  the  weight 
of  that  atom. 

If  we  take  a  given  quantity  of  hydrogen,  we 
can  tell  you  what  weight  of  any  substance  it  is 
equal  to,  and  we  may  state  this  in  pounds,  ounces, 
grains,  or  in  the  metric  system  as  litres,  decilitres, 
grammes,  milligrammes,  and  so  on.  But  in  chemis- 


50          NITROGEN   AND    HYDROGEN 

try  the  weight  of  an  atom  of  hydrogen  was  until 
recently  always  the  standard.  Latterly  it  has  been 
proposed  to  take  an  atom  of  oxygen  as  the  standard 
of  weight,  simply  because  this  gives  for  other  sub- 
stances numbers  easier  to  handle. 

When  we  consider  the  make-up  of  various  sub- 
stances and  find  that  the  innumerable  compounds 
in  nature  or  in  the  laboratory  can  be  simplified, 
analyzed,  or  taken  apart,  into  a  few  elements,  we 
are  led  to  ask  whether  as  we  learn  more  about 
chemistry  and  become  more  skilful  in  reducing 
substances  to  their  simplest  form,  we  shall  not  at 
last  be  able  to  show  that  all  things  are  different 
forms  of  a  very  few  substances  or  elements,  much 
fewer  than  the  eighty  now  considered  to  be  simple, 
uncompounded  elements.  We  may  in  imagination 
go  even  further  and  ask  whether  we  shall  not  come 
to  a  time  when  we  shall  know  all  substances  to  be 
only  various  forms  of  a  single  element.  Many  think, 
as  already  stated,  that  if  this  time  should  ever 
come,  this  single  element  will  be  hydrogen. 


CHAPTEE    IV 

PROPERTIES  OF  MATTER 

THE  first  requisite  in  studying  any  substance  is 
to  get  it  into  its  simplest  form.  Matter  is  defined 
in  books  upon  physics  as  being  anything  that  can 
occupy  space.  Physics  also  teaches  that  all  mat- 
ter is  divisible,  or  separable,  into  portions.  But, 
for  all  that  we  can  say,  the  defining  of  matter  is 
impossible,  except  by  telling  what  it  does.  Perhaps 
the  easiest  form  of  words  in  which  we  can  put 
the  thought  is  that  which  defines  matter  as  being 
"anything  that  resists  force."  A  little  careful 
thought  will  show  that  we  can  know  matter  only 
where  it  resists  some  action  of  a  force,  as  by  being 
felt,  seen,  or  otherwise  known  by  the  senses,  by 
changing  the  action  or  direction  of  a  force,  as  inter- 
rupting light  or  sound,  and  so  on. 

So  far  as  we  know  matter,  it  is  constantly  di- 
visible, and  we  have  given  names  to  these  different 
degrees  of  division.  If  we  take  a  substance  and 
crush  it  to  the  finest  powder,  the  properties  of  each 


52  PROPERTIES    OF    MATTER 

particle  remain  unchanged.  We  may  make  these 
particles  still  finer  by  dissolving  them  in  a  liquid, 
or  often  we  may  melt  them,  or  by  heat  convert  them 
into  a  vapor  or  gas. 

Take  for  an  illustration  the  substance,  water, 
which  we  have  learned  consists  of  hydrogen  and 
oxygen.  We  may  cause  it  to  disappear  by  apply- 
ing gentle  heat,  thus  changing  it  to  an  invisible 
vapor;  or,  by  a  greater  heat,  we  may  convert  it 
into  steam,  or  by  cold  we  may  turn  it  into  solid 
ice,  and  that  ice  may  be  melted  again  into  water. 

Yet  we  know  by  experiment  that  the  tiniest  par- 
ticles of  water  may  be  brought  back,  unchanged, 
into  a  liquid  form. 

We  know  also,  from  chemical  experiment,  that 
the  most  minute  of  these  divisions  of  water  must 
contain  two  elements,  hydrogen  and  oxygen. 

For  these  different  divisions  of  a  substance  chem- 
ists have  made  names  whereby  to  follow  substances 
in  thought,  even  where  they  cannot  be  traced  by 
the  senses. 

These  names  are  as  follows :  To  the  smallest  pos- 
sible portions  of  a  substance  that  still  remain  un- 
divided into  elements,  and  consequently  unchanged 
in  its  properties,  the  name  molecule  has  been  given. 


PROPEKTIES    OF    MATTER  53 

This  word  means,  in  Latin,  "  little  body."  For  the 
still  smaller  portions  that  make  up  such  a  mole- 
cule, that  is,  in  the  case  of  water,  for  the  tiniest 
portions  of  the  two  gases  that  go  together  to  form 
the  water  molecule,  the  name  atom  has  been  made. 
Thus  we  say  that  the  molecule  of  water  contains 
atoms  of  hydrogen  and  oxygen.  When  we  succeed 
in  obtaining  the  smallest  possible  portion,  or  mole- 
cule, of  a  chemical  element,  or  non-compound  body, 
there  is  reason  to  believe  that  this  too  is  made 
up  of  atoms,  even  though  each  of  these  atoms  be 
the  same  element  as  the  molecule. 

We  must  remember,  therefore,  that  all  matter  is 
considered  to  be  divisible,  first  into  molecules,  and 
then  into  the  atoms  that  go  to  make  the  molecule. 
This  also  implies  that  some  molecules  are  made  up 
of  atoms  that  differ  from  it  and  from  one  another, 
while  other  molecules  are  made  up  of  atoms  that 
possess  the  same  properties  as  the  molecule. 

The  reason  why  chemists  have  come  to  think  of 
matter  in  this  way  is  because  it  explains  to  them 
and  makes  clear  to  our  minds  the  different  forms 
in  which  matter  exists,  and  also  explains  how  sub- 
stances are  made  up  chemically.  The  ordinary 
forms  of  matter  known  to  all  of  us  have  already 


54  PKOPEKTIES    OF    MATTER 

been  mentioned  in  speaking  of  water,  as  solid, 
liquid,  and  vapor — ice,  water,  and  steam.  Nearly 
everything  appears  to  us  either  as  solid,  liquid,  or 
gas,  and  since  we  have  seen  that  many  common 
substances  are  very  easily  changed  from  one  of  these 
forms  to  another,  we  have  come  to  believe  that 
these  result  only  from  a  change  of  condition. 

Again,  water  is  the  most  familiar  illustration. 
We  know  that  it  is  only  a  question  of  how  much 
heat  exists  in  water,  whether  we  shall  see  it  in  the 
form  of  ice,  or  being  converted  to  its  melted  form, 
as  a  liquid ;  and  by  still  further  heat  we  know  it  to 
be  changed  to  a  vapor. 

But  to  explain  these  three  states  of  matter  it  is 
believed  that  the  strength  of  attraction  holding  the 
molecules  together  is  what  governs  the  state  of  the 
substance.  When  the  molecules  cling  closely  to- 
gether and  are  not  easily  separated,  the  substance 
is  a  solid.  When  this  force  is  much  weakened  so 
that  the  molecules,  though  somewhat  held  together, 
yet  may  be  readily  movable,  the  substance  takes 
the  liquid  form.  The  force  being  still  further  weak- 
ened, the  substance  presents  itself  as  a  gas ;  and  in 
this  state  either  holds  together  with  only  the  slight- 
est union,  or  even  tends  to  separate  in  all  direc- 


PROPEKTIES    OF    MATTER  55 

tions.  The  study  of  these  conditions  belongs  not 
strictly  to  chemistry,  but  to  physics.  But  a  knowl- 
edge of  them  must  be  attained  in  order  that  we  may 
follow  the  theories  upon  which  chemists  work. 

When  we  come  to  dealing  with  the  changes  that 
affect  the  relations  of  the  smaller  portions,  that 
is,  of  the  atoms,  we  leave  the  science  of  physics 
and  enter  upon  that  of  chemistry. 

Chemistry  has  to  do  mainly  with  those  changes 
in  which  the  molecules  are  separated  into  atoms. 
Remember  that  we  have  said  the  molecule  is  the 
smallest  possible  portion  of  a  substance  that  can 
retain  its  properties.  If,  now,  this  smallest  por- 
tion be  further  broken  up  into  atoms,  we  shall  know 
it  by  a  change  in  the  properties  of  the  substance 
treated. 

When  we  shall  have  reached  the  state  in  which 
we  deal  with  atoms,  chemistry  will  show  the  laws 
by  which  these  atoms  go  together  again  to  make 
new  compounds.  By  means  of  chemistry,  then,  we 
are  able  to  do  two  things :  First,  to  take  apart  the 
molecules  of  substances,  and  second,  to  put  together 
the  atoms  which  have  been  in  these  molecules  so  as 
to  make  molecules  of  new  substances.  The  laws 
of  the  action  of  atoms  in  separating  and  combining, 


56  PKOPERTIES    OF    MATTER 

and  the  methods  by  which  they  may  be  taken  apart 
and  put  together,  and  also  the  nature  of  their 
arrangement,  and  the  force  that  causes  them  to 
remain  together  or  to  be  separated — these  are  the 
field  of  chemistry. 

There  are  in  every  science  two  great  divisions. 
These  are  known  as  the  "  theory  "  and  the  "  prac- 
tice "  ( or,  as  they  are  sometimes  called,  the  science 
and  the  art).  The  theory  of  any  science  is  that 
part  of  it  which  forms  the  answer  in  any  case  to  the 
question  "  Why?  "  The  practice  in  the  same  way 
answers  to  the  question  "How?  "  If  we  find,  for 
example,  that  by  putting  a  fire  under  a  vessel  of 
water,  the  water  gradually  begins  to  boil,  as  we  say, 
"  boils  away,"  we  have  learned  something  that  re- 
lates to  practice.  We  have  learned  how  to  change 
water  into  vapor.  It  is  not  necessary  that  we 
should  know  why  the  result  is  brought  about,  so 
long  as  we  are  satisfied  with  the  result  alone. 

But  as  soon  as  we  begin  to  wish  to  bring  about 
any  result  in  the  best  possible  way,  we  must  inquire 
why  a  certain  course  of  action  causes  the  result; 
and  in  the  case  of  the  water,  we  ask  why  heat 
should  make  water  boil  and  then  disappear.  The 
answer  to  the  question  "  How?  "  is  usually  a  sim- 


PROPERTIES    OF    MATTER  57 

pie  one.  It  can  be  found  out  by  experiment. 
Once  having  found  out,  we  may  usually  repeat  the 
work  as  often  as  we  choose.  But  the  question 
"  Why?  "  lies  deeper,  and  sometimes  cannot  be  an- 
swered at  all.  The  answer  to  it  is  in  all  cases 
merely  a  guess — an  attempt  to  explain  more  or  less 
fully  and  satisfactorily.  If  we  find  that  our  ex- 
planation or  theory  makes  it  possible  to  foretell 
what  will  happen  in  new  cases,  then  we  may  safely 
trust  it  and  believe  in  it. 

This  whole  matter  of  molecules  and  atoms  is  one 
of  theory.  None  of  our  senses  can  enable  us  to 
know  directly  either  molecules  or  atoms.  We  can 
only  imagine  that  they  exist,  and  then  give  rea- 
sons why  their  existence  makes  clear  to  us  the 
action  of  elements  or  of  compounds  one  upon  the 
other. 

It  would  be  a  long,  dry,  and  difficult  task  to  set 
out  all  the  reasons  why  this  belief  in  molecules 
and  atoms — known  as  the  atomic  theory — has  been 
accepted  by  nearly  all  men  of  science.  It  is  not 
even  yet  complete  or  fully  understood,  but  the  be- 
lief in  and  knowledge  of  its  laws  have  made  it  pos- 
sible to  do  so  many  wonderful  things  that  those 
who  doubt  it  are  few  indeed. 


58  PROPERTIES    OF    MATTER 

This  theory  serves  not  only  to  explain  many 
otherwise  mysterious  facts  in  chemistry,  but  also 
in  physics,  in  medicine,  in  botany — in  the  whole 
circle  of  the  sciences.  It  makes  us  see  a  reason  for 
the  rules  and  laws  by  which  light,  sound,  electricity, 
and  heat,  act  and  may  be  controlled.  It  is  desira- 
ble, therefore,  to  get  into  our  minds  a  clear  notion 
of  matter,  that  is,  of  all  substances,  as  explained  by 
the  atomic  theory.  Many  great  philosophers  have 
told  us  good  ways  of  picturing  the  nature  of  the 
theory  to  our  minds.  They  ask  us  to  suppose  that 
a  single  drop  of  water  could  be  enlarged  until  it 
were  as  big  as  our  earth;  then,  it  is  believed,  the 
molecule  might  be  perhaps  somewhere  near  the  size 
of  a  tennis-ball.  And  these  molecules  themselves 
would  be  made  up  of  still  smaller  atoms.  This  is 
not  mere  guesswork,  but  is  based  on  careful  figur- 
ing by  Sir  William  Thomson  (Lord  Kelvin),  who 
knew  more  of  such  matters  than  almost  anybody. 

Until  very  recently  it  was  believed  that  the  atom 
was  indivisible  and  represented  the  very  smallest 
portions  of  matter  with  which  science  had  to  deal. 
But  especially  after  the  discovery  of  the  X-rays  by 
Professor  Roentgen,  careful  study  of  their  action 
convinced  the  scientific  men  that  the  ray  was  made 


PROPERTIES    OF    MATTER  59 

up  of  a  stream  of  moving  particles  of  matter,  much 
smaller  even  than  the  atoms.  This  came  to  be  be- 
lieved because  of  their  going  directly  through  so 
many  kinds  of  matter.  They  would  penetrate  even 
sheets  of  metal.  Then  experiments  were  made  to 
find  out  what  these  inconceivably  minute  particles 
weighed,  and  experiments  led  to  the  conclusion  that 
they  weighed  but  one-thousandth  as  much  as  a 
single  atom  of  hydrogen. 

It  is,  of  course,  not  to  be  expected  that  in  a  book 
of  this  sort  these  complicated  experiments  can  be 
fully  explained.  We  will  say  only  that  the  measur- 
ing and  weighing  of  the  velocity  and  the  mass  of 
these  particles  was  done  by  causing  them  to  move 
aside  from  their  regular  lines  of  motion  by  means 
of  a  magnet.  Then  it  was  calculated  what  their 
velocity  and  weight  must  be  in  order  to  be  bent  a 
certain  amount  from  their  paths  by  the  knpwn  at- 
traction of  the  magnet. 

So,  to-day,  we  have  come  to  believe  that  from  the 
atom  itself  can  be  separated  something  still  smaller. 
Sir  Oliver  Lodge,  another  great  English  philoso- 
pher, has  told  us  something  of  what  these  minutest 
forms  of  matter  are  thought  to  be.  The  name  given 
to  them  is  "  electrons."  If  we  imagine  an  atom 


60  PROPERTIES    OF   MATTER 

enlarged  to  the  same  enormous  degree  as  we  have 
already  imagined  the  enlarging  of  a  molecule,  then, 
Sir  Oliver  Lodge  tells  us,  it  would  be  found  to 
consist  of  a  few  electrons — that  is,  few  in  propor- 
tion to  the  space  they  would  then  fill — flying  about 
in  orbits  much  as  the  planets  move  about  the  sun. 
Supposing  that  the  atom  had  been  enlarged  until 
it  were  as  big  as  a  great  house,  then  the  size  of 
each  electron  might  be  compared  to  that  of  a 
printed  period,  or  the  smallest  dot  that  you  could 
make  with  a  sharp  pencil-point. 

If  the  atoms  in  a  single  drop  of  water  are  so  tiny 
that  enlarging  a  drop  of  water  to  the  size  of  this 
earth  might  make  each  atom  no  larger  than  a  ten- 
nis-ball ;  and  then  if  we  could  imagine  each  of  these 
tennis-balls  magnified  until  it  were  as  big  as  a 
church,  in  which  case  the  electrons  it  contained 
would  be  no  more  than  the  tiniest  dat — you  may 
imagine  fo*  yourself  the  inconceivable  smallness 
of  these  electrons,  hundreds  of  which  are  found  in 
every  atom.  The  pencil  dot  you  made  to  represent 
an  electron  must  in  reality  contain  millions  of 
electrons,  yet  you  must  not  think  of  these  as  packed 
closely  together.  They  are,  in  proportion  to  their 
including  space,  as  far  apart  as  the  planets  in  the 


PKOPERTIES    OF   MATTEK  61 

solar  system.  They  are  in  motion  with  unimagin- 
able rapidity. 

Exactly  in  what  paths  they  move  we  cannot  tell. 
They  seem  to  be  repelling  one  another  and  attempt- 
ing to  get  as  far  apart  as  possible.  It  is  believed 
that  they  are  kept  together,  that  is,  kept  from  flying 
outside  the  limits  of  an  atom,  by  electricity.  It  is 
believed,  for  reasons  too  long  to  give  here,  that  all 
the  electrons  are  negatively  electrified.  Now,  like 
electricities  repel,  and  so  electrons  repel  one  an- 
other. But  it  is  believed  that  within  each  atom 
there  is  something  positively  electrified,  which, 
therefore,  attracts  the  negative  electrons  and  keeps 
them  revolving  about  it,  just  as  the  sun  attracts 
the  planets  and  keeps  them  from  flying  off  into 
space.  Whether  the  electric  forces  of  which  we 
are  talking  are  connected  with  some  portion  of 
matter,  or  whether  they  consist  of  nothing  except 
the  motion  of  the  ether,  is  not  yet  known. 

To  understand  what  is  meant  by  motions  of  the 
ether,  let  us  suppose  a  great  body  of  water  in  which 
there  are  numberless  and  tiny  whirlpools  moving 
with  enormous  force.  You  know  that  the  water 
coming  from  the  hose  of  a  fire-engine  or  of  a  mining 
hose  travels  so  fast  that  it  cannot  be  penetrated. 


62  PROPERTIES    OF    MATTER 

If  you  try  to  strike  a  stick  through  one  of  these 
streams,  the  stick  will  rebound  as  if  it  had  hit 
metal.  If  you  imagine  the  currents  of  the  little 
whirlpools  travelling  with  something  like  that  ra- 
pidity, you  will  see  that  you  could  not  push  some- 
thing into  them.  They  would  indeed  resist  as  if 
they  were  solid.  Now,  it  is  believed  that  the  elec- 
trons are  in  swiftest  motion  within  each  atom  of  a 
substance,  and  that  they  resist  the  attempt  of  any- 
thing to  come  between  them,  just  as  a  stream  of 
water  resists  the  entrance  of  a  stick.  Sir  Oliver 
Lodge,  in  speaking  of  the  atom  of  hydrogen,  the 
lightest  of  all,  supposes  that  it  may  contain  per- 
haps seven  hundred  electrons,  half  negative,  half 
positive.  If  this  number  may  be  accepted,  then 
an  atom  of  oxygen,  which  is  sixteen  times  heavier, 
might  be  thought  of  as  containing  eleven  or  twelve 
thousand  electrons,  and  so  on  with  the  other  ele- 
ments, each  containing  as  many  electrons  as  its 
weight  would  indicate  when  compared  with  the 
weight  of  hydrogen. 

He  also  warns  us  that  though  science  has  de- 
tected these  negative  electrons  in  certain  rays,  the 
positive  "  electron  "  is  only  imagined,  having  never 
been  detected  separate  from  some  atom.  This  same 


PROPERTIES    OF    MATTER  63 

theory  carried  out  would  lead  us  to  believe  in  the 
possibility  that  all  elements  are  made  up  of  the 
same  kind  of  electrons,  differing  only  in  their  num- 
ber, and  possibly  in  their  kind  of  motion. 

Remember  that  all  this  is  only  a  belief;  but 
it  is  a  belief  that  helps  us  to  understand  and  ex- 
plain by  the  laws  of  electricity  alone  many  of  the 
actions  of  elements  on  one  another,  chemically,  that 
would  otherwise  be  very  complex  and  mysterious. 
Thus  it  is  believed  that  all  light  comes  from  the 
setting  free  of  negative  electrons.  They  pass  out 
from  their  atoms  and  shoot  through  space.  When 
they  are  released  from  atoms  with  slower  speed, 
they  become  evident  to  us  as  heat.  When  released 
in  another  way,  they  are  known  as  electric  action. 
By  the  same  theory — the  escape  of  electrons  and 
their  striking  against  other  substances — is  ex- 
plained what  is  known  as  radio-activity,  or  the  emis- 
sion of  different  forms  of  rays,  as  from  radium  and 
other  substances. 

To  show  how  recent  these  views  are,  it  was  only 
in  1903  that  scientific  men  decided  radio-activity 
was  likely  to  consist  in  the  flinging  away  of  atoms 
positively  electrified.  These  atoms  have  been 
weighed  and  seem  to  be  somewhat  near  the  weight 


64  PROPERTIES    OF    MATTER 

of  an  atom  of  hydrogen,  and  they  are  accompanied 
by  the  negative  electrons,  only  %0oo  as  large. 

One  need  not  try  to  follow  too  closely  the  com- 
plicated thinking  of  the  philosophers  on  these  sub- 
jects. It  is  enough  that  we  bear  it  in  mind  that  all 
matter  is  believed  to  be  made  up,  first,  of  molecules 
representing  its  own  smallest  portions;  that  these 
molecules  are  made  up  of  atoms  closely  held  to- 
gether, and  that  the  atoms  themselves  are  made  up 
of  electrons  moving  in  orbits  with  inconceivable 
rapidity  round  about  some  central  portion.  Such 
is  the  latest  view  of  the  make-up  of  all  substances, 
and  to  it  we  must  now  and  again  refer  in  order  to 
explain  chemical  laws. 

In  talking  of  the  three  forms  of  matter  we  have 
explained  how,  as  heat  is  applied,  a  solid  is  changed 
to  liquid,  and  the  liquid  to  a  vapor  or  gas.  But 
what  we  have  been  explaining  in  regard  to  the 
make-up  of  molecules  and  atoms  prepares  us  to 
understand  what  is  meant  by  philosophers  and 
chemists  who  nowadays  talk  of  the  "  fourth  state  " 
of  matter.  In  a  gas  the  molecules  tend  to  sepa- 
rate from  one  another.  If  this  separation  be  car- 
ried still  further,  so  that  the  molecules  themselves, 
or  even  the  atoms  of  a  single  element,  are  broken 


PROPERTIES    OF    MATTER  65 

up  into  the  electrons,  then  we  shall  have  a  new,  or  a 
fourth,  state  of  matter,  with  laws  of  its  own  differ- 
ing from  those  of  the  other  three.  Concerning  this 
fourth  state,  we  know  as  yet  less  than  of  the  other 
three,  and  it  is  at  this  time  being  most  busily 
studied  in  many  laboratories. 

It  is  especially  interesting  because  to  this  state 
of  matter  belong  the  various  new  kinds  of  light  rays 
whose  action  is  so  wonderful  and  was  until  the 
last  few  years  so  unaccountable.  As  a  result  of 
this  whole  method  of  thinking  of  matter  under  the 
atomic  theory,  we  must  regard  the  world,  and  the 
universe  itself,  as  being  made  up  of  almost  unim- 
aginably tiny  portions,  each  of  which  is  eternally 
in  motion  of  inconceivable  rapidity.  Thus  it  will 
be  seen  that  the  old  idea  of  "  dead  matter "  has 
been  entirely  abandoned.  Everything  is  in  motion, 
and  science  is  little  more  than  the  study  of  these 
movements. 

We  may  also,  as  a  result  of  these  theories,  under- 
stand why  it  is  that  some  scientific  men  believe  that 
all  the  other  elements  may  be  nothing  more  than 
different  forms  of  hydrogen;  and  for  this  reason. 
Hydrogen  is  the  lightest  of  all  matter.  If  we  are 
trying  to  find  that  of  which  all  other  matter  is  made 


66  PEOPERTIES    OF    MATTER 

up — taking  it  for  granted  that  there  is  one  such 
universal  element — then  it  is  hard  to  escape  the 
conclusion  that  this  one  element  must  be  that  of 
which  the  atom  is  the  lightest  of  all  things;  for 
surely  this  atom  cannot  be  made  up  of  larger  atoms 
if  each  one  of  them  is  heavier  than  itself. 

To  repeat  the  argument:  Admitting  all  things 
have  weight,  if  any  one  thing  be  simple  and  all  the 
rest  compound,  every  conceivable  compound  must 
be  heavier  than  the  one  simple  thing,  since  whatever 
is  added  to  that  simplest  and  lightest  substance 
must  make  it  heavier.  If  this  reasoning  be  just, 
then  it  would  seem  hydrogen  is  that  element  which 
is  the  foundation  of  all  the  others. 

In  the  same  way  it  may  be  argued  that  since  elec- 
trons are  lighter  than  the  hydrogen  atom,  they  may 
be  either  the  simplest  form  of  matter,  or  something 
different  from  matter.  Then  at  a  certain  point, 
as  matter  is  being  separated,  it  ceases  to  be  matter 
when  it  is  separated  into  electrons.  Of  course,  to 
say  that  electrons  are  not  matter  is  to  consider 
them  only  as  forms  of  motion  in  the  ether. 

We  have  already  said  that  while  the  science  of 
physics  deals  with  molecules,  or  with  substances 
whose  properties  do  not  change  enough  to  change 


PKOPERTIES    OF   MATTER  67 

their  identity,  chemistry  deals  with  atoms,  and 
studies  substances  having  regard  to  the  atoms  of 
which  they  are  made  up,  and  the  changes  in  sub- 
stances that  are  made  by  changing  the  atoms  that 
compose  them.  It  must  be  remembered,  however, 
that  even  in  chemistry  we  deal  ordinarily  with  sub- 
stances in  molecules,  since  the  changes  brought 
about  by  separating  and  combining  atoms  are  not 
possible  to  observe.  The  atoms  do  not  remain  in  a 
free  state.  No  sooner  are  they  set  free  from  one 
combination  than  they  enter  into  another. 


OF   THE 

UNIVERSITY 

OF 


CHAPTER   V 

THE  ELEMENTS.    THE  LAWS  OF  COMBINATION 

IN  order  that  record  may  be  kept  of  these  changes 
of  atoms,  and  also  that  they  may  be  understood  and 
followed,  there  is  a  system  of  notation  and  of  nam- 
ing. The  chemical  elements  have  each  assigned  to 
them  a  simple  symbol.  Ordinarily  the  symbol  of 
an  element  is  the  first  letter  of  its  name,  but  where 
this  would  make  confusion,  other  letters  may  be 
added.  Some  of  the  older  elements  are  still  called 
by  their  Latin  names,  and  the  initial  is  taken  from 
the  Latin  word.  Each  of  these  symbols  stands  not 
only  for  the  element,  but  for  one  atom  of  that  ele- 
ment. If  we  wish  to  express  more  than  one  atom, 
a  number  is  put  before  the  symbol. 

To  take  as  illustrations  elements  of  which  we 
have  already  learned  something,  oxygen  has  the 
symbol  O,  which  means  one  atom  of  oxygen.  For 
nitrogen  in  the  same  way  we  have  the  symbol  N, 
and  for  hydrogen  the  symbol  H,  the  letter  standing 
in  each  case  for  a  single  atom.  If  we  wish  to  ex- 


70  THE    ELEMENTS 

press  more  than  a  single  atom,  we  put  a  number 
before  it.  Thus  4  O  would  stand  for  four  atoms  of 
oxygen.  When  the  atoms  are  in  a  compound,  the 
figures  expressing  their  number  is  written  after  the 
symbol  and  may  be  made  smaller  and  either  higher 
up  or  lower  down.  Thus  the  well-known  symbol 
for  water  is  H2O  or  H2O,  meaning  two  atoms  of 
hydrogen  combined  with  one  atom  of  oxygen  be- 
cause water  is  so  composed.  Students  of  algebra 
will  see  that  this  sort  of  notation  is  like  that  in 
algebra,  being  no  more  than  the  use  of  co-efficients 
and  exponents. 

Having  this  way  of  writing  the  names  of  elements 
in  compounds,  it  is  easy  to  express  any  substance 
chemically.  To  do  this  we  have  only  to  put  the 
chemical  elements  that  enter  into  it  side  by  side. 
There  is  no  rule  as  to  the  order  in  which  the  ele- 
ments are  to  be  written,  but  certain  orders  have  be- 
come usual.  Thus  OH2  would  likewise  mean  water, 
but  it  is  not  commonly  so  written. 

Just  as  a  symbol  represents  one  atom,  so  a  for- 
mula represents  one  molecule.  To  express  more 
than  one  molecule,  the  number  of  them  is  written 
before  the  formula.  Thus  to  write  four  molecules 
of  water,  we  put  it  thus :  4H2O.  Where  no  figure 


THE    ELEMENTS  71 

follows  a  symbol  in  a  formula,  the  figure  1  is,  of 
course,  understood.  Thus  HC1  would  mean  one 
atom  of  hydrogen  combined  with  one  atom  of  chlor- 
ine, and  the  whole  formula  means:  one  molecule 
of  hydrochloric  acid,  as  will  be  understood  later. 

Certain  methods  that  are  used  in  algebra  may  be 
extended  to  the  writing  of  formulae  in  chemistry. 
For  example,  if  a  compound  acts  as  if  it  were  an 
element,  this  is  sometimes  expressed  by  putting  it 
into  a  parenthesis,  or  by  separating  the  formula 
into  groups  by  inserting  a  period.  If  a  group  of 
atoms  is  to  be  repeated  several  times,  it  may  be 
enclosed  in  a  parenthesis  and  a  small  figure  put 
after  it,  just  as  if  it  were  a  single  symbol.  If  the 
whole  formula  is  to  be  multiplied,  remember  that 
the  large  figure  precedes  it  all. 

In  order  to  express  the  fact  that  certain  chemical 
actions  take  place,  it  is  usual  to  write  them  in 
equations,  which  are  read  exactly  as  if  they  were 
arithmetical  or  algebraic — that  is,  from  left  to 
right.  As  the  formula  of  any  compound  shows  the 
number  of  atoms  that  are  combined  to  make  a  mole- 
cule of  that  compound,  and  as  no  atom  can  ever  be 
destroyed  in  making  new  compounds,  a  correct 
chemical  equation  must  always  be  equal  on  the  two 


72  THE    ELEMENTS 

sides;  that  is  to  say,  if  the  number  of  atoms  on  one 
side  are  added  together,  they  must  equal  the  num- 
ber of  atoms  on  the  other  side.  Likewise,  if  we 
add  together  the  weights  of  atoms  in  any  compound, 
we  shall  have  the  weight  of  its  molecule,  since  the 
formula  represents  one  molecule.  In  an  equation, 
likewise,  the  weight  of  the  molecules  put  together 
must  equal  the  weight  of  the  molecules  produced. 

In  order,  therefore,  to  use  chemical  equations,  it 
is  necessary  for  us  to  know  the  weight  of  each  of 
the  atoms.  To  the  finding  out  of  these  weights  for 
each  of  the  elements  has  been  devoted  labor  unim- 
aginable, by  countless  chemists ;  and  many  of  them 
are  still  somewhat  uncertain.  But  for  most  of  the 
elements,  they  are  wonderfully  accurate. 

Three  tables,  giving  important  facts  about  the 
elements — first,  a  list  of  those  that  should  be  very 
familiar,  then  of  those  less  well  known,  and  then 
of  rarer  ones,  are  given  on  pages  74  and  75.  Be- 
sides these  there  are  many  still  rarer,  which  will 
be  found  in  a  complete  table  at  the  end  of  the  book. 

This  writing  of  chemical  equations  and  the  ex- 
pressing of  chemical  compounds  by  means  of  let- 
ters and  numbers  has  been  of  the  utmost  value.  It 
has  led  men  to  record  and  to  remember  the  make-up 


THE    ELEMENTS  73 

of  compounds,  and,  still  more  important,  has  led 
to  the  discovery  of  the  laws  by  which  compounds 
are  made.  It  was  thus  ascertained  that  when  a 
compound  was  separated  into  its  elements,  these 
elements  were  always  found  to  exist  in  precisely 
the  same  proportion  in  the  same  compound.  Thus 
in  the  case  of  common  salt,  chloride  of  sodium,  as 
it  is  called  chemically,  no  matter  how  much  or  how 
little  salt  was  separated  into  sodium  and  chlorine, 
the  relation  of  the  amounts  of  these  two  to  one 
another  never  changed.  Sodium  chloride  has  this 
formula,  NaCl,  and  from  what  we  have  already 
said,  you  will  understand  that  each  molecule  is 
made  up,  therefore,  of  one  atom  of  sodium  to  one 
of  chlorine.  But  the  atomic  weight  of  sodium  is 
22.88,  chlorine  is  35.18,  and  the  weights  of  the 
sodium  and  chlorine  in  any  amount  of  salt  will 
always  be  to  one  another  in  the  proportion  that 
these  numbers  bear.  Thus  in  58  ounces  of  salt, 
there  would  be  a  little  over  22  ounces  of  chlorine 
and  a  little  over  35  ounces  of  sodium.  If  there 
were  58  tons,  or  58  grains,  the  proportions  of  the 
two  elements  would  not  be  changed,  and  if,  on  the 
contrary,  we  were  to  put  together  sodium  and  chlor- 
ine to  make  salt,  the  two  elements  would  combine 


74  THE    ELEMENTS 


§• 

r^o 


s 


o  >. 


OOO-*  G»  t-«5  fc-t-ODOS 

OOOt-        COC5>-i«5OT*OCO        «O  O5t-«5XOQO«5i-HC5 


cc 


C»Ci 


H  1-1  M  0)  «5 


i-HOiOiOOi         >-H         G*  CM  G*  CO  CO  CO      CO      t-C*> 


£2 

w 


0 


•S      5 

" 


2-3MNc«;^« 


a   ?_      7    I 


_»  —    ^"S  £>.  •  _» 

si  I  II  ll   I     fa   »  * 

SB      m§2j      ^gali^l         >5=      H      S 

||||s|fl|   fll^5|l|    ilslll  i It 

Miiiiiiiliiiiri       1  ii 


THE    ELEMENTS 


75 


O 


s? 


0    X    CO    -H       H 


O 


g 


§  *§3    Bfl 

lillllllll 


g  I  § 

°      3      G 

III 


Tj* 
O  l-H 


«5      fc-      W         b- 

I-H      I-H      O         *O 
05      «5      CD         O 


QQ 


3   3    $ 
s   s   1 


M    U    O 


I 

O 


a        s 

d  .2    S     I 
g    S  .3    »3 

llll 


76  THE    ELEMENTS 

with  one  another  in  these  same  proportions  only. 
If  there  was  more  of  one  or  the  other,  it  would 
simply  be  left  uncombined,  for  lack  of  a  partner  or 
set  of  partners. 

This  is  what  has  become  known  as  the  Law  of 
Definite  Proportions.  The  law  of  definite  propor- 
tions was  found  by  Proust.  It  was  seen  that  it 
did  not  in  all  cases  explain  the  action  of  the  ele- 
ments, for  at  times  the  elements,  though  combining 
in  definite  proportions,  combined  in  several  propor- 
tions. By  further  observation,  however,  it  was  dis- 
covered by  John  Dalton  that  when  an  element  com- 
bined in  more  than  one  proportion,  the  larger  pro- 
portion was  always  a  multiple  of  the  smaller. 
Thus,  supposing  that  the  oxygen  atom  be  repre- 
sented by  its  combining  weight,  16,  when  it  com- 
bined in  other  proportions  than  16  it  was  found 
that  these  were  multiples  of  the  number  16 ;  that 
is,  it  combined  in  16,  in  32,  in  48,  or  in  64,  parts,  as 
if  1,  2,  3,  or  4  of  its  atoms  combined  with  other 
elements  as  if  they  were  but  a  single  atom.  When 
this  law  was  recognized  by  Dalton,  it  became  known 
as  the  Law  of  "  Multiple  Proportions."  * 

*  In  the  combining  of  gases,  advantage  is  taken  of  the  fact 
that  they  have  been  discovered  to  combine  in  "  volumes  in  simple 


THE    ELEMENTS  77 

This  it  was  that  laid  the  foundations  of  modern 
chemistry. 

Upon  these  laws  scientific  study  of  all  compounds 
were  based,  for  with  them  combination  became  a 
matter  of  fixed  laws,  not  of  untraceable  chance. 

We  shall  now  return  to  our  study  of  the  ele- 
ments, taking  up  next  that  most  important  one, 
carbon,  because  of  its  abundance. 

ratios  to  each  other  and  to  the  volume  of  the  product."  That  is, 
their  relation  is  expressed  by  small  whole  numbers.  Their 
volumes  also  are  believed  to  contain,  at  the  same  heat  and 
pressure,  the  same  number  of  molecules.  Thus  they  are  com- 
pared with  hydrogen,  and  weighed  volume  for  volume.  This 
gives  the  ratio  of  their  weight  to  hydrogen — as  will  be  explained 
later. 


CHAPTER   VI 

COAL  AND  CABBON 

COAL  is  so  important  a  part  of  our  civilization 
that,  when  only  a  few  years  ago,  a  strike  on  the  part 
of  the  coal  miners  at  that  time  put  an  end  to  the 
production  of  coal  and  caused  it  to  become  very 
scarce,  it  seemed  as  if  there  was  no  part  of  our 
daily  life  that  did  not  depend  upon  it.  Yet  it  is  a 
substance  that  was  almost  unknown  a  few  gener- 
ations ago.  It  is  true  that  in  books  written  about 
that  time  we  see  occasional  references  to  the  use 
of  coal  in  an  open  grate,  to  make  a  luxurious  fire, 
but  it  was  not  looked  upon  as  a  necessity.  Ordinary 
heating  was  done,  where  it  was  done  at  all,  by  burn- 
ing wood.  The  work  of  the  world  was  performed 
either  by  man  or  animal  power,  or  by  mills  driven 
by  wind  or  water.  It  was  the  increasing  scarcity 
of  wood  and  the  increasing  value  of  the  steam-en- 
gine that  suddenly  gave  to  the  deposits  of  coal  an 
enormous  value  and  set  mankind  to  getting  it  out 
of  the  earth  in  great  quantities. 

79 


80  COAL   AND    CARBON 

Being  so  much  used,  it  was  also  more  deeply 
studied,  but  in  spite  of  all  research  that  has  gone 
to  determine  its  origin,  and  of  all  the  experimental 
science  bent  upon  it,  coal  even  to-day  remains  more 
or  less  of  a  mystery.  The  earliest  idea  considered  it 
a  mineral,  which,  of  course,  in  a  sense  it  is,  but 
not  in  the  sense  that  granite  or  flint  is  a  mineral. 
It  is,  rather,  a  mineral  in  the  sense  that  chalk  is 


FOSSIL  FOUND  IN  A  COAL  BED 

so-called — that  is,  it  is  the  remains  of  animal  or 
vegetable  life. 

The  next  belief  that  man  held  about  it  saw  in  it 
the  compressed  vegetable  substances  of  past  ages — 
the  wood  and  the  leaves  of  old  forests.  This  was 
a  step  nearer  the  truth,  or  what  we  now  hold  to 
be  the  truth.  For,  undoubtedly,  coal  consists  of 
the  remains  of  former  vegetation,  but  instead  of  be- 
ing mainly  the  product  of  an  age  wherein  flourished 


COAL   AND    CAKBON  81 

great  forests  such  as  we  now  have,  it  is  believed  that 
coal  is  made  up  for  the  most  part  of  the  pollen  dust 
that  for  thousands  upon  thousands  of  years,  during 
the  carboniferous  age,  was  deposited  from  the 
gigantic  ferns  and  similar  plants  that  grew  with 
amazing  luxuriance  in  those  hot,  moist,  and  abso- 
lutely windless  ages. 

Whatever  may  have  been  its  origin,  to  the  chem- 
ist coal  is  a  veritable  storehouse  of  treasures.  It 
consists,  it  is  true,  to  a  very  large  extent  of  carbon 
— the  same  substance  that  in  other  forms  we  know 
as  the  "  black  lead  "  of  pencils  (which  nowadays  is 
graphite,  a  nearly  pure  carbon)  and  in  the  diamond, 
which  is  simply  pure  carbon  in  crystal  form.  But, 
in  addition  to  its  greater  proportion  of  carbon,  coal 
has  given  rise  to  a  vast  number  of  other  products. 
By  being  raised  to  a  high  heat  in  a  closed  vessel, 
the  coal  may  be  separated,  or  distilled,  so  as  to  give 
off  fumes  from  which  may  be  obtained  various  com- 
pounds and  elements. 

We  have  already  said  that  coal  is  a  vegetable 
product,  and  that  it  consists  largely  of  carbon. 
And  the  same  is  true  of  all  vegetable  matter.  Car- 
bon is  the  foundation  upon  which  all  animal  and 
vegetable  tissues  are  built  up.  Owing  to  a  strange 


82  COAL   AND    CARBON 

peculiarity  of  the  element,  carbon,  it  has  the  ability 
to  enter  into  an  almost  unending  number  of  com- 
pounds. So  complex  are  these  and  so  puzzling,  that 
in  the  science  of  chemistry  the  study  of  carbon  com- 
pounds has  been  set  apart  as  a  separate  branch. 
For  many  years,  in  the  earlier  days  of  the  science, 
it  was  believed  that  a  large  part  of  these  compounds 


SECTION  OF  COAL  AS  SEEN  THEOUGH  A  MICROSCOPE 

could  not  be  formed  in  the  absence  of  animal  life; 
that  is,  they  must  be  the  result  of  vital  forces.  It 
was  therefore  thought  they  were  produced  only  in 
the  tissues  of  living  animals  or  vegetables.  At  a 
later  date,  however,  chemists  began  to  form  these 
substances  in  the  laboratory,  and  what  had  been 
called  "  organic  chemistry  "  (that  is,  the  chemistry 
of  organic  life)  was  studied  under  a  new  name — the 
"  chemistry  of  carbon  compounds." 


f  *J 

I      fl  *,  Uj-ts 

M1  Illfll 

s^ei  ^s:sns 
!f§*i 


I  Ell 


;2B-1  lefSjiii 

^tlis  ^tif.ji 

55||||LI||||1 

gl^f*!r^*«l 
0<wg-«I*l5^less'M5< 

Miif!ifif!A 


ai;iiii:i*:i"'. 


IJ!8!l2M:Ipi 
llmiaal"8. 

!e    ||«8«fl$ill 

^    -S^afS  S  ""^J1*  ° 

•ififCliltZfi 


20  .§H2 

3S.I"§    ' 
£.2 


84  COAL   AND    CAKBON 

This  little  introduction  will  show  that  it  is  at 
present  impossible  to  enter  into  any  thorough  chem- 
ical consideration  of  coal.    We  introduce  the  men- 
tion of  it  in  this  place  only  to  bring  in  some  con- 
sideration of  the  element  carbon  on  account  of  its 
importance  in  all  that  concerns  human  life.     You 
will  be  prepared  already  to  understand  something 
of  the  reason  for  the  value  of  coal  as  a  fuel.    Car- 
bon, combining  readily  with  oxygen,  yet  combines 
slowly  enough  to  keep  up  the  chemical  action  that 
gives  us  warmth,  steadily,  effectively,  and  without 
attention.     Illuminating  gas  was  for  a  long  time 
derived  exclusively  from  coal,  being  distilled  from 
it,  and  sent  where  needed.     The  combination  of 
heat  in  so  portable  and  effective  a  form,  with  a 
light  so  easily  managed,  almost  recreated  indus- 
tries.    By  means  of  light  the  hours  of  labor  were 
lengthened,  and  the  new  fuel  meant  an  enormous 
multiplication  of  man's  power.     And  this  whole 
change,  you  must  mark,  was  due  to  chemistry. 
Coal  was  no  more  than  a  convenient,  cheap,  and 
readily  obtained  form  of  the  element  carbon;  and 
this  element,  together  with  the  ones  we  have  already 
spoken  of,  hydrogen,  oxygen,  and  nitrogen,  make 
up  a  great  part  of  all  animal  and  vegetable  sub- 


Copyright,  by  Underwood  &  Underwood,  New  Yvrk. 

DINNER  Two  AND  ONE-HALF  MILES  UNDERGROUND. 


COAL   AND    CARBON  85 

stances.  These,  then,  are  the  four  great  elements, 
and  a  knowledge  of  these  four  forms  the  basis  upon 
which  practical  chemistry  must  ever  be  built  up. 

We  have  already  seen  how,  by  means  of  burning 
wood  without  allowing  too  much  oxygen  to  reach 
it,  charcoal — another  less  pure  form  of  carbon — 
is  produced.  This  will  help  us  to  understand  how 
the  light,  soft  pollen,  dropping  for  centuries  to  the 
ground  in  undisturbed  layers,  and  being  then  car- 
ried underground  or  overlaid  by  rocks  and  new  soil, 
which  must  have  been  deposited  by  earthquakes, 
by  seas,  or  by  other  agencies  at  a  later  time,  was 
subjected  to  pressure  that  consolidated  the  pow- 
dery substances  into  a  solid  mass,  and  at  the  same 
time,  owing  to  the  heat  produced  by  pressure,  to 
some  extent  oxidized  these  layers  of  vegetable  sub- 
stance and  separated  them  from  such  elements  as 
the  heat  would  drive  off.  The  result  was  what  may 
be  called  a  slow  oxidizing,  or  burning.  Owing  to 
the  lack  of  oxygen  beneath  the  earth,  this  burning 
acted  much  as  the  slow  burning  of  the  charcoal- 
maker's  fire,  and  produced  likewise  a  sort  of  rock 
charcoal — what  we  know  as  coal. 

It  is  now  believed  that  compounds  of  carbon  are 
subject  to  precisely  the  same  laws  that  govern  all 


86 


COAL   AND    CAKBON 


others.  Though  we  still  speak  of  "  organic  "  com- 
pounds, we  do  so  in  a  different  sense.  The  term 
no  longer  means  compounds  that  cannot  be  met 
with  except  in  some  living  organism,  but  simply 


SECTION  OF  PART  OF  EAETH'S  CRUST  NEAR  MAUCH  CHUNK,  PENN., 
SHOWING  LAYERS  OF  COAL 

denotes  such  as  are  usually  found  there.  As  it 
happens,  carbon  enters  into  these,  forming  a  vast 
number  of  them  which  are  related  to  one  another, 
and  therefore  are  usually  studied  together.  When 
it  is  remembered  that  these  organic  compounds  in- 
clude all  vegetable  products,  such  as  sugar,  starch, 
alcohol,  honey ;  and  all  those  animal  products  that 
are  used  in  industries,  such  as  horn,  leather,  meat, 
wax — it  will  be  seen  that  practical  life  depends 
largely  upon  them.  Though  they  are  so  various 
in  appearance  and  qualities,  yet  they  contain  for 
the  most  part  only  a  few  elements,  the  four  we  have 
already  mentioned  being  the  chief. 


COAL   AND    CARBON  87 

To  take  a  few  examples,  starch  and  fruit  juices 
contain  carbon,  hydrogen,  and  oxygen.  Meat  con- 
tains, in  addition  to  these  three,  nitrogen,  and  other 
animal  substances  may  contain  also  sulphur  or 
phosphorus.  When  chemists  make  up  new  com- 
pounds, such  as  dye-stuffs  or  extracts  for  various 
purposes,  these  may  contain  almost  any  of  all  the 
elements,  depending  upon  the  properties  desired. 
As  we  know  something  already  of  the  other  ele- 
ments mentioned,  we  may  give  some  attention  here 
to  the  characteristics  of  carbon. 

It  is  found  pure  in  nature,  as  in  the  diamond 
and  graphite,  and  nearly  pure  in  charcoal  or  coal. 
In  combination,  we  have  already  said  it  is  nearly 
universal,  being  an  essential  part  of  wood,  cotton, 
wax,  starch,  albumen  (or  white  of  egg) ,  bones  of  all 
animals,  and  also  many  minerals,  among  which  may 
be  mentioned  limestone,  chalk,  and  marble.  The 
purest  carbon,  the  diamond,  will  give  us  some  idea 
of  the  qualities  of  the  element.  It  is  the  hardest 
of  all  substances;  weighs  three  and  a  half  times  as 
much  as  the  same  bulk  of  water;  no  liquid  at  any 
ordinary  temperature  will  dissolve  it;  yet,  in  spite 
of  its  hardness,  it  is  brittle,  and  may  be  readily 
shattered.  The  proof  that  the  diamond  is  pure  car- 


88  COAL   AND    CAKBON 

bon  consists  in  burning  the  stone  in  pure  oxygen. 
After  a  diamond  has  been  entirely  consumed,  there 
will  remain  a  gas,  which  analysis  shows  to  be  car- 
bon dioxide — a  combination  of  carbon  atoms  with 
oxygen  atoms. 

A  still  stronger  proof  was  given  by  a  French 
chemist,  Moissan.  This  chemist  dissolved  pure 
charcoal,  or  carbon,  in  melted  iron.  This  solution 
was  then  poured  into  water,  which  cooled  the  sur- 


face of  the  mass  of  iron,  caused  it  suddenly  to  con- 
tract, and  thus  brought  an  enormous  pressure  to 
bear  upon  the  carbon  dissolved  in  the  iron.  After 
the  iron  was  cut  apart,  crystallized  carbon  was 
found  inside,  and  tests  of  every  sort  showed  that 
these  crystals  were  diamonds,  that  is,  were  pure 
carbon. 

It  has  already  been  said  that  carbon  occurs  in 
three  forms,  as  diamond,  graphite,  and  in  the  less 


COAL   AND    CAKBON  89 

pure  forms  found  in  coal,  charcoal,  soot,  and  other 
such  charcoal-like  remains  of  combustion.  The 
diamond  and  the  graphite  are  carbon  crystallized, 
which  means  that  they  have  been  formed  by  car- 
bon dissolved  or  melted  and  then  allowed  to  cool, 
in  which  case  it  takes  regular  forms,  as  do  such 
substances  as  sugar,  salt,  and  alum.  With  graph- 
ite the  ordinary  lead-pencil  has  made  us  familiar. 


ABTIFICIAL  DIAMONDS    (ENLABGED)   PBEPABED  BY  MOISSAN. 

While  the  diamond  is  the  hardest  of  all  things,* 
graphite  is  soft  enough  to  leave  a  mark  even  on 
paper  or  the  fingers.  It  is  much  lighter  than  dia- 
mond, and  is  very  useful  in  the  arts  because  of  its 
great  resistance  to  heat.  It  can  be  dissolved  like 
other  forms  of  carbon  in  melted  metals. 

Of  coal  we  have  already  spoken,  but  we  may  add 
to  what  has  been  said  that  it  occurs  in  three  or 
more  widely  differing  varieties.  When  hardest,  it 
is  known  as  anthracite ;  a  softer  sort  is  the  bitumi- 

*  Carbide  of  boron   is   mentioned   as   a  possible  exception   in 
Smith's   "  General   Inorganic   Chemistry." 


90  COAL   AND    CAKBON 

nous,  which  is  less  pure  than  the  anthracite,  con- 
taining more  substances,  such  as  oils,  that  are  not 
pure  carbon.  A  still  softer  sort  of  coal  is  lignite, 


MOISSAN'S  ELECTBIC  FURNACE  FOE  MAKING  DIAMONDS 
Moissan's  description  of  this  furnace  is  as  follows :  "  It 
consisted  of  two  bricks  of  quicklime  placed  one  on  top  of  the 
other.  The  lower  brick  contained  a  long  longitudinal  groove  to 
receive  the  two  electrodes  [carbon  rods],  and  situated  in  the 
centre  was  a  small  cavity.  This  cavity  might  vary  in  size,  and 
contained  a  bed  some  centimeters  in  depth  of  the  substance  to 
be  acted  upon  by  the  heat  of  the  arc,  or  a  small  crucible  of 
carbon  containing  the  substance  to  be  treated  may  be  placed 
there.  The  upper  brick  was  slightly  hollowed  out  in  the  part 
just  above  the  arc.  As  the  intense  heat  of  the  current  soon 
melted  the  surface  of  the  lime,  giving  it,  at  the  same  time,  a 
beautiful  polish,  a  dome  was  obtained  in  this  way  which  re- 
flected all  the  heat  onto  the  small  cavity  which  contained  the 
crucible." 

which  appears  to  be  formed  of  vegetable  substance 
that  has  not  been  reduced  so  nearly  to  carbon  alone. 
Peat  is  even  softer  than  lignite,  and  has  not  really 
been  formed  into  coal,  though  it  may  be  an  earlier 


COAL  AND  CARBON 


91 


stage  of  the  same  process  that,  continued,  would 
result  in  coal  formation. 

Ordinary  charcoal  may  be  produced  from  almost 
any  kind  of  animal  or  vegetable  matter  that  is 
partly  consumed,  that  is,  combined  with  oxygen 
so  as  to  leave  a  large  part  of  the  carbon  unchanged. 
If  soft  coal  be  burned  much  as  wood  is  burned  in 
making  charcoal,  the  substance  that  remains  is 


VERTICAL  SECTION  OF  MOISSAN'S  ELECTRIC  FURNACE.     EE  ARE 

THE   ELECTRODES 

This  shows  the  furnace  with  the  parts  slightly  separated.  The 
furnace  is  small,  some  being  only  16  to  18  cm.  (about  7  in.) 
long,  15  cm.  wide,  and  14  cm.  high.  The  carbon  rods  are  from 
1  to  5  cm.  in  diameter. 

known  as  coke,  which  is  about  nine-tenths  carbon, 
but  harder  and  heavier  than  ordinary  wood-char- 
coal. It  is  used  in  many  industries,  since  it  burns 
with  a  smokeless,  intense  heat,  and  contains  little 
sulphur  or  other  volatile  substances  that  are  harm- 
ful in  such  processes  as  making  iron. 
The  three  main  forms  of  carbon  are,  nevertheless, 


92  COAL   AND    CAKBON 

all  the  same  substance.  The  difference  in  their  form 
and  quality  is  believed  to  be  due  to  the  fact  that 
the  molecules  in  each  case  contain  a  different  num- 
ber of  atoms.  This  character  of  assuming  different 
forms  without  a  change  of  substance  is  known  in 
chemistry  as  allotropism,  from  allos,  another,  and 
tropos,  a  form.  Sulphur  is  another  element  that 
shows  allotropism. 

Owing  to  the  fact  that  carbon  is  so  widely  found 
and  forms  compounds  that  exist  in  all  living  things 
— plants  and  animals — a  later  chapter  must  take 
up  the  methods  in  which  its  compounds  are  formed. 
But  in  an  elementary  book  only  the  most  general 
account  of  carbon's  manifold  compounds  can  be 
given. 


CHAPTEE   VII 

NATURE  OF  CHEMICAL  COMBINATIONS 

WE  have  learned  that  burning  is  to  be  under- 
stood as  a  combining  of  oxygen  with  some  other 
element.  There  is  no  attempt  to  explain  why  such 
combining  takes  place.  We  only  know  that  once 
certain  elements  are  raised  to  a  certain  degree  of 
heat  they  begin  to  form  new  compounds  with  the 
oxygen,  giving  rise  to  substances  of  entirely  differ- 
ent properties  from  those  that  have  been  burned. 

But  this  is  not  the  only  example  of  such  com- 
pounds. ,  Things  can  be  burned  in  other  gases  than 
oxygen.  Chlorine  will  thus  combine  with  hydrogen 
and  form  an  acid  known  as  hydrochloric  acid. 
Both  copper  and  iron  may  be  caused  to  unite  with 
the  vapor  of  sulphur,  giving  copper  sulphide,  or 
iron  sulphide.  Other  chemical  combinations  are 
formed  by  simply  bringing  together  solutions,  or 
solids  and  solutions,  of  different  elements.  Thus 
if  we  put  pieces  of  zinc  into  hydrochloric  acid  we 
will  find  that  the  zinc  will  drive  the  hydrogen  from 

93 


94  CHEMICAL   COMBINATIONS 

its  compound  with  the  chlorine,  forming  a  chloride 
of  zinc,  while  the  hydrogen  is  set  free. 

All  these  changes  depend  upon  qualities  that  are 
known  as  "  chemical  affinity,"  which  is  another  way 
of  saying,  chemical  liking.  The  reasons  for  this 
affinity  are  not  known  with  any  certainty.  We 
can  only  say  that  under  some  circumstances  a 
substance  has  a  stronger  attraction  for  one  sub- 
stance than  for  another,  and  thus  when  compounds 
are  brought  together  there  is  a  change  of  partners, 
as  it  were.  The  changes  in  compounds  thus  brought 
about  are  known  as  double  decomposition,  for  the 
simple  reason  that  two  compounds  when  brought 
together  are  both  separated  and  then  new  com- 
pounds are  formed  from  the  partners.  Thus,  if 
oxygen  and  mercury  exist  in  one  compound,  and 
chlorine  and  hydrogen  in  another,  by  bringing  them 
together  they  exchange  partners,  the  hydrogen  and 
oxygen  uniting  to  form  water,  while  the  mercury 
and  chlorine  also  join  forces,  making  mercury 
chloride. 

It  is  also  true  that  certain  compounds  are 
strongly  Joined  and  are  difficult  to  separate  into 
their  elements,  and  that  others  seem  to  be  joined 
by  a  weaker  bond  and  readily  separate.  Thus  it 


CHEMICAL   COMBINATIONS  95 

is  enough  to  heat  certain  compounds  slightly  to 
bring  about  a  change  in  their  composition.  Others 
will  not  be  separated  until  we  have  found  some  ele- 
ment having  for  one  of  the  partners  an  attraction 
exceeding  that  for  its  partner  in  the  first  com- 
pound. 

Thus  it  happens  that  the  chemist  in  bringing 
about  changes  is  not  always  certain  beforehand 
just  what  will  take  place.  Sometimes  by  knowing 
which  elements  strongly  attract  others,  he  can  fore- 
tell just  what  new  compounds  will  be  made.  In 
other  cases  he  cannot  be  certain  until  the  experi- 
ment has  been  tried. 

Two  elements  which  seem  to  have  an  exceedingly 
strong  attraction  for  one  another  are  hydrogen  and 
oxygen.  Consequently  whenever  compounds  con- 
taining hydrogen  and  oxygen  are  brought  together 
it  is  very  likely  that  the  hydrogen  and  oxygen  atoms 
will  join,  forming  water.  Understanding  this,  we 
may  see  the  reason  for  a  very  common  result  in  the* 
mixing  of  two  compounds  in  liquid  form.  If  one 
contains  hydrogen  and  the  other  oxygen,  and  each 
contains  also  two  substances  that  together  form  a 
solid,  a  mixture  of  the  two  first  compounds  will 
result  in  combining  the  hydrogen  and  oxygen, 


96  CHEMICAL    COMBINATIONS 

whereupon  the  remaining  partners  will  be  left  to 
unite  into  a  solid,  and  the  result  of  the  experiment 
will  form  a  solid  (in  fine  particles)  floating,  or  dif- 
fused, in  water.  The  chemical  change  being  com- 
plete, we  may  then  allow  the  mixture  to  settle,  or 
may  filter  it,  and  in  this  way  the  water  may  be 
poured  off,  leaving  the  solid.  If  the  solid  is  one 
that  will  not  float  and  is  allowed  to  settle,  it  is 
known  as  a  precipitate. 

It  will  surprise  not  even  the  youngest  reader  to 
be  told  that  there  is  practically  no  limit  to  the  num- 
ber of  chemical  compounds.  There  are  seventy  or 
eighty  elements,  and  while  a  few  of  these  are  not 
ready  to  make  combinations,  and  a  number  of  them 
are  very  rare,  at  least  twenty  of  them  are  very  im- 
portant, and  many  of  these  are  exceedingly  common. 
If  the  reader  will  reflect  upon  the  number  of  words 
that  may  be  composed  out  of  the  twenty-six  let- 
ters of  the  alphabet,  he  will  gain  some  idea  of  the 
almost  infinite  number  of  possible  chemical  com- 
pounds, to  say  nothing  of  the  mixtures  of  these  or 
of  their  different  states,  as  solids,  liquids,  and  gases. 
Fortunately,  however,  the  larger  part  of  these  com- 
pounds may  be  generally  classed  under  a  few  head- 
ings, and  the  more  important  of  these  agree  in  cer- 
tain general  characters.  The  names  of  these 


CHEMICAL    COMBINATIONS  97 

classes  are  more  or  less  familiar  to  us  all  from 
daily  use.  Thus  we  know  that  chemicals  are 
divided  into  acids,  bases,  and  salts.  Although 
these  three  do  not  include  all  chemical  compounds, 
they  are  convenient  names  under  which  to  group 
the  larger  part.  The  acids,  for  example,  were  so 
called  because  in  this  sort  of  compound  the  early 
chemists  detected  a  sour  taste.  Acids  also  changed 
the  color  of  many  vegetable  substances,  and  are  for 
the  most  part  active  compounds  ready  to  enter  into 
chemical  changes.  The  bases  are  such  compounds 
as  when  acted  upon  by  acids  form  salts.  Their 
character  will  be  explained  later. 

The  acids  all  contain  hydrogen,  and  most  of  them 
contain  also  oxygen.  It  was  at  first  believed  that 
oxygen  was  the  maker  of  acids,  and  the  gas  was 
named  from  this  belief.  But  it  has  been  found  out 
that  hydrogen  is  the  essential  element  in  acids. 
Joined  with  the  hydrogen  (or  hydrogen  and  oxy- 
gen), to  make  an  acid,  is  always  some  other  element 
among  those 'known  as  the  non-metals,  examples  of 
which  are  sulphur,  chlorine,  phosphorus,  and  nitro- 
gen. The  bases  contain  oxygen,  usually  hydrogen, 
and  always  a  metal ;  and  elements  which  form  bases 
are  ranked  with  the  metals.  The  salts  contain  a 
metal,  a  non-metal,  and  most  of  them  also  oxygen. 

I 


98  CHEMICAL   COMBINATIONS 

It  is  the  chemical  relation  of  these  three  classes 
of  compounds  that  really  fix  their  classification. 
Thus  when  an  acid  and  a  base  are  made  to  act 
upon  one  another,  they  destroy  more  or  less  each 
other's  properties,  and  the  result  is  a  compound 
having  few  or  none  of  the  properties  like  those  of 
the  two  that  formed  it.  This  resulting  compound 
is  a  salt.  For  example,  if  we  add  hydrochloric 
acid  to  sodium  hydroxide,  the  result  may  be  written 
in  the  following  formula : 

HC1  +  NaOH  ==  NaCl  +  H2O 

the  meaning  of  which  is  that  hydrochloric  acid  is 
neutralized  by  the  sodium  hydroxide,  and  that  the 
result  is  sodium  chloride  (common  salt)  and  water. 
In  this  case  we  have  an  acid,  combined  with  a  base 
(NaOH),  and  the  result  is  a  salt.  The  metal, 
sodium,  has  taken  the  place  of  the  hydrogen  in 
the  acid,  while  the  hydrogen  of  the  acid  is  com- 
bined with  the  hydrogen  and  oxygen  of  the  base, 
forming  water.  Something  more  of  this  action  is 
told  later,  in  speaking  of  electrolysis  and  solu- 
tions. 

Let  us  now  look  a  little  more  closely  into  the 
nature  of  acids,  bases,  and  salts. 


CHEMICAL   COMBINATIONS  99 

Although  the  definition  of  an  acid  is  not  an  easy 
thing  to  write  in  simple  terms,  yet  the  nature  of 
an  acid  may  be  readily  understood  from  a  few  sim- 
ple examples.  An  acid  in  general  is  strong  in  its 
action,  attacking — that  is,  changing — the  compo- 
sition of  compounds,  or  taking  into  its  own  compo- 
sition atoms  of  other  elements.  The  commoner 
acids  are  sulphuric,  nitric,  and  acetic.  The  acids 
themselves  occur  as  solids,  liquids,  and  gases,  but 
most  of  them  are  soluble  in  water,  and,  ordinarily 
speaking,  it  is  this  solution  that  we  mean  by  an 
"acid."  When  the  acid  is  very  strong,  or  mixed 
with  little  water,  it  must  be  handled  with  the 
greatest  care,  since  its  action  is  rapid  and  destruc- 
tive. When  much  diluted,  the  action  is  of  course 
slower  and  the  other  qualities  are  likewise  dimin- 
ished, and  the  solution  may  be  more  safely  han- 
dled. 

The  way  in  which  acids  are  ordinarily  recog- 
nized in  the  laboratory  is  by  means  of  a  test  with 
what  is  known  as  "  litmus  "  paper.  This  is  a  paper 
containing  vegetable  juices  procured  from  a  species 
of  lichen.  This  juice  stains  the  paper  a  soft  blue 
color,  but  when  dipped  into,  or  touched  by,  the 
acid,  the  blue  is  changed  to  a  pink  or  reddish  tinge. 


100          CHEMICAL   COMBINATIONS 

Having  been  so  changed,  it  may  be  restored  to  its 
original  color  by  being  dipped  into  an  alkali.  This 
is  a  delicate  test  and  a  very  convenient  one.  It 
may  be  familiar  to  young  readers,  since  it  is  used 
in  photographic  operations  to  determine  whether 
certain  baths,  as  those  used  in  toning  prints,  are 
acid  or  alkaline. 

The  sour  taste  of  acids  is,  when  not  too  strong, 
very  agreeable  to  the  palate,  and  has  led  to  the 
use  of  many  substances  for  food  because  of  the  acid 
they  contain.  Vinegar  is  water  flavored  with 
acetic  acid;  pickles  contain  the  same  acid;  lemon 
juice  and  other  fruit  juices  are  relished  because  of 
the  fruit  acid  in  them.  Milk,  when  it  turns  sour, 
does  so  because  it  forms  an  acid — lactic  acid. 

With  these  few  examples,  let  us  see  what  the 
chemists  say  in  the  attempt  to  define  an  acid  in 
chemical  terms.  The  books  tell  us  that  an  acid 
is  "a  compound  containing  hydrogen  that  can  be 
replaced  by  a  metal."  The  meaning  of  this  is  that 
when  a  compound  so  acts  upon  a  metal  as  to  give 
up  hydrogen  and  to  replace  this  by  atoms  separated 
from  the  metal,  this  compound  is  to  be  classed  with 
the  acids.  But  although  no  one  ignorant  of  chem- 
istry would  think  of  calling  water  an  acid,  under 


CHEMICAL    COMBINATIONS          101 

this  definition  it  must  be  so  called;  for  water,  in 
acting  upon  certain  metals,  will  give  up  hydro- 
gen and  produce  an  oxide  of  those  metals.  For 
this  reason  chemists  agree  that,  rightly  speaking, 
water  should  be  regarded  as  an  acid,  although  it 
does  not  affect  the  color  of  litmus  paper. 

In  the  early  days  of  chemistry  it  was  believed 
that  the  important  element  in  all  acids  was  oxygen, 
but  as  time  went  on  and  further  experiments  were 
made  and  understood,  compounds  were  found  that 
certainly  must  be  considered  as  acids,  and  yet  were 
entirely  free  from  oxygen.  Hydrochloric  acid 
(HC1)  is  an  example.  It  is  for  this  reason  that 
the  definition  given  above,  making  hydrogen  the 
chief  element  in  the  defining  of  acids,  was  adopted. 

Nevertheless,  it  is  true  that  most  acids  do  con- 
tain oxygen,  and  the  ordinary  names  of  the  varie- 
ties of  acids  and  of  the  substances  resulting  from 
their  action  are  based  upon  the  amount  of  oxygen 
contained  in  the  acids.  To  that  form  of  an  acid 
which  is  best  known  is  given  a  name  ending  with 
the  letters  ic.  Thus  an  acid  made  up  of  sulphur, 
hydrogen,  and  oxygen  (H2SO4),  is  known  as  sul- 
phuric acid.  But  another  acid  can  be  formed  from 
these  same  elements  containing  less  oxygen,  so  the 


102          CHEMICAL   COMBINATIONS 

ending  of  its  name  changes,  and  it  is  called  sul- 
phurous acid.  If  a  third  form  has  still  less  oxygen, 
it  is  named  by  putting  hypo  before  the  names  end- 
ing in  ous,  as,  hyposulphurous  acid.  This  word, 
hypo,  is  from  the  Greek,  and  means  under. 

In  the  same  way  we  may  form  the  names  nitric 
and  nitrous  acid,  or  chloric,  chlorous,  and  hypo- 
chlorous.  If,  however,  there  be  a  form  of  any  acid 
containing  even  more  oxygen  than  the  commonest 
and  best  known  form,  this  is  expressed  by  the  pre- 
fix per  added  to  the  ic  form.  In  this  way  we  have 
persulphuric  acid  and  perchloric  acid. 

These  can  be  remembered  by  simply  recalling 
that  per  means  more,  hypo  means  less,  ic  is  at- 
tached to  the  commonest  acid,  and  ous  to  one  that 
is  weaker  in  oxygen. 

Owing  to  the  peculiar  chemical  qualities  of  car- 
bon, acids  in  which  carbon  is  an  important  element 
are  not  named  precisely  according  to  this  system, 
but  they  end  ordinarily  in  ic. 

These  names  are  chemical  names,  but  there  exist 
also  "trade,"  or  commercial,  names  for  some  of 
these  acids.  A  list  of  these  common  terms  is  given 
in  the  last  chapter. 

The  word  base  is  used  in  chemistry  to  mean  the 


CHEMICAL    COMBINATIONS  103 

class  of  substances  which  neutralize  acids;  that  is 
to  say,  which,  when  caused  to  combine  with  the 
acid,  will  destroy  its  properties.  Most  of  these  are 
solids,  but  just  as  we  in  speaking  of  "  acids,"  usu- 
ally have  in  mind  the  solution  of  these  substances 
in  water,  so  in  speaking  of  bases  we  often  mean 
such  as  may  be  made  into  solutions  that  will  neu- 
tralize the  acids.  Examples  of  such  bases  are  lime, 
ammonia,  sodium,  and  potassium.  When  these  are 
referred  to  with  their  property  of  neutralizing  acids 
in  mind,  they  are  commonly  called  "alkalies." 
They  are  tested  by  means  of  litmus  paper,  and  have 
the  property  of  restoring  to  the  reddened  paper  its 
blue  color.  Generally  speaking,  a  base  is  a  sub- 
stance derived  from  a  metal  by  the  action  upon  it 
of  hydrogen  or  oxygen,  and  having  the  property  of 
combining  with  an  acid  to  form  a  salt.  Ammonia, 
however,  does  not  contain  a  metal,  and  yet  is  a 
base,  for  it  contains  a  combination  of  elements 
(NEU)  that  acts  as  a  metal.  A  name  often  applied 
to  certain  bases  is  "  hydroxides,"  or  hydrates.  This 
name  is  given  because  most  of  them  contain  hydro- 
gen and  oxygen.  By  putting  before  the  term,  hy- 
droxides, the  name  of  the  metal  from  which  it  is 
derived,  we  distinguish  the  base.  Thus  we  have 


104          CHEMICAL   COMBINATIONS 

sodium  hydroxide,  calcium  hydroxide,  calcium  hy- 
drate (slaked  lime),  and  so  on. 

When  an  acid  and  a  base  are  caused  to  combine, 
each  loses  its  properties  and  enters  into  a  new  com- 
pound not  like  either.  Compounds  resulting  thus 
from  the  action  of  an  acid  and  a  base  are  known  as 
salts — probably  from  their  resemblance  in  many 
properties  to  common  salt  (which  is,  chemically, 
chloride  of  sodium).  Most  salts  are  soluble  in 
water,  and  when  such  solution  is  made,  it  will  be 
found  that  litmus  paper  may  be  dipped  in  it  with- 
out changing  color.  Thus  the  acid  which  would 
have  changed  the  paper  red,  and  the  base  which 
would  have  turned  it  blue,  have  now  united  into  a 
substance  which  has  neither  effect.  The  salt,  there- 
fore, is  said  to  be  neither  acid  nor  alkaline,  but 
"neutral." 

Salts  are  not  the  only  neutral  substances;  neither 
are  all  salts  neutral.  Nevertheless  the  general  rule 
is  as  stated.  The  name  salt  is  also  applied  to  cer- 
tain substances  produced  otherwise  than  by  the 
action  of  an  acid  on  a  base,  since  the  name  is  used 
only  as  a  convenient  way  of  classing  certain  com- 
pounds together. 

The  names  of  different  salts  have  been  given  in 


CHEMICAL   COMBINATIONS          105 

such  a  way  as  to  show  which  class  of  acid  gave  rise 
to  them.  The  acids  ending  in  "ic  "  form  salts  end- 
ing in  "  ate."  Thus  sulphuric  acid  acting  on  zinc 
would  give  zinc  sulphate.  But  those  ending  in 
"  ous  "  form  "  ites  " ;  Sulphurous  acid  forms  sul- 
phites.  If  the  prefix  hypo  or  per  occurs  in  an  acid, 
it  appears  also  in  the  name  of  the  salt.  Thus  a  per- 
chloric acid  would  give  a  perchlorate;  and  hypo- 
sulphurous  acid  would  give  a  hyposulphite — a  name 
which  will  be  recognized  by  photographers  as  be- 
longing to  the  well-known  fixing  solution,  which  is 
a  hyposulphite  of  soda.  That  is  to  say,  it  is  formed 
by  hyposulphurous  acid  acting  upon  the  base, 
sodium,  to  make  the  salt,  hyposulphite  of  soda.* 

Where  a  salt  contains  only  two  elements,  the 
name  ends  in  ide,  this  being  affixed  to  the  non- 
metallic  element.  Thus  the  salt  is  known  as  a  bro- 
mide, chloride,  sulphide,  and  so  on,  depending  upon 
the  element  upon  which  the  action  of  the  acid  has 

*  This  illustration  may  be  retained,  although,  strictly  speak- 
ing, the  fixing  solution  is  chemically  called  "  sodium  thiosul- 
phate."  This  syllable,  thio,  indicates  that  this  special  salt  is 
the  result  of  the  action  of  thiosulphuric  acid  on  sodium,  and 
thiosulphuric  acid  indicates  an  acid  containing  more  sulphur 
and  less  oxygen  than  sulphuric  acid.  This,  however,  does  not 
affect  the  reason  for  the  old  name  of  hyposulphite  of  sodium. 


106          CHEMICAL   COMBINATIONS 

taken  place.  Where  hydro  occurs  in  the  name  of 
the  acid,  it  is  omitted  when  the  name  of  the  salt 
ending  in  ide  is  given.  Thus  we  have  in  the  name 
for  common  salt,  sodium  chloride,  the  fact  that  it 
is  produced  by  the  action  of  hydrochloric  acid  upon 
sodium,  and  that  it  is  a  compound  of  only  two 
elements,  which  we  know  because  it  ends  in  ide. 
The  prefix  hydro  is  not  necessary  when  only  two 
elements  are  in  the  salt,  because  it  is  known  that 
the  hydrogen  or  oxygen  from  the  original  acid 
have  combined  into  water,  since  neither  of  them 
has  entered  into  the  salt.  If  either  were  in  the 
salt  it  would  have  more  than  two  elements.  Thus 
to  produce  common  salt  the  hydrochloric  acid  has 
separated  and  given  its  chlorine  to  the  sodium, 
making  chloride  of  sodium.  This  is  the  equation : 

HC1  +  Na  =  NaCl  +  H 

Showing  that  one  atom  of  hydrogen  is  set  free,  or, 
it  may  be,  is  taken  up  by  oxygen  to  form  water. 


CHAPTER  VIII 

ABOUT  COMMONER  ELEMENTS 

FORTUNATELY  for  those  who  wish  to  know  a  little 
something  about  chemistry  without  too  much  deep 
study,  the  elements  that  are  commonest  are  not 
very  numerous,  and  even  with  these  commoner  ele- 
ments we  can  aid  our  memories  by  grouping  them 
into  certain  families,  or  classes,  the  members  of 
which  resemble  one  another  in  their  action  and  in 
their  properties.  Thus  one  wide  grouping  is  caused 
by  a  division  into  metals  and  non-metals,  another 
into  the  acids  and  the  bases,  and  the  salts. 

When  certain  elements  are  united  with  hydrogen 
and  oxygen  to  make  compounds,  some  of  them  will 
be  found  to  belong  to  the  acid  compounds  and 
others  to  the  base  compounds,  and  the  base-forming 
compounds  include  what  we  know  as  metals,  and 
also  certain  other  elements  that  are  called  metals 
because  they  are  grouped  with  these.  This  causes 
the  other  group  of  elements,  the  acid-forming 
group,  to  be  referred  to  as  non-metals. 

107 


108      ABOUT    COMMONER    ELEMENTS 

It  is  not  true,  however,  that  this  distinction  al- 
ways holds,  for  a  few  elements  may,  with  hydrogen 
and  oxygen,  form  compounds  sometimes  of  one  kind 
and  sometimes  of  another.  But  these  matters  may 
be  mentioned  in  the  case  of  each  element. 

For  the  reasons  given,  chemists  have  for  a  long 
time  put  the  elements  into  groups,  of  which  we  may 
consider  the  following  as  principal  ones:  first, 
hydrogen,  which  though  it  may  be  considered  a 
non-metal,  stands  alone,  making,  as  it  were,  a  group 
by  itself,  for  no  other  element  bears  a  very  close 
relation  to  it.  Next,  oxygen,  which,  although  not 
strongly  related  to  any  other  element,  yet  has  some 
resemblance  in  the  character  of  its  compounds  with 
the  element,  sulphur,  and  therefore  may  be  thought 
of  with  it.  Next  comes  a  group  of  four  elements, 
the  halogens  or  "  salt-makers,"  which  includes 
chlorine,  bromine,  iodine,  and  fluorine ;  then  one  of 
three,  including  sulphur,  selenium,  and  tellurium. 
To  this  group  oxygen  is  sometimes  added.  An- 
other group  of  four  is  the  nitrogen  family:  nitro- 
gen, phosphorus,  arsenic,  and  antimony;  then  fol- 
lows a  family  of  two  members,  carbon  and  silicon. 

We  have  not  named  all  the  members  of  these 
families,  but  given  only  the  commoner  elements 


ABOUT    COMMONER    ELEMENTS      109 

belonging  to  them.  All  these  elements  named  be- 
long to  the  larger  class  already  spoken  of  as  the 
"non-metals"  (see  List  of  Elements  in  last  chap- 
ter), except  that  one  of  the  metals,  a  member  of  the 
nitrogen  family  (antimony)  also  forms  bases,  and 
thus  acts  like  a  non-metal. 

In  order  to  get  some  idea  of  the  character  of 
these  elements,  we  shall  tell  something  of  the  action 
of  each  group  separately,  taking  up  first  the  chlo- 
rine family — for  we  have  already  spoken  of  hydro- 
gen and  oxygen. 

THE  CHLORINE   FAMILY,  OR   HALOGENS 

This  family  has  a  special  name  of  its  own.  The 
members  of  it  are  called  halogens.  This  term  comes 
from  the  Greek  words,  hals  (aAs)  and  (y«^s). 
Hals  means  salt,  genes  means  producer;  so  the 
group  is  known  as  salt-makers. 

s 

CHLORINE 

Chlorine,  the  first  of  these,  is  a  gas  at  the  ordi- 
nary temperature.  It  was  first  prepared  in  1774 
by  the  German  chemist,  Scheele.  Since  chlorine 
readily  combines  with  a  great  many  common  sub- 
stances, it  is  not  found  in  nature  except  in  com- 


110      ABOUT    COMMONER    ELEMENTS 

pounds,  the  commonest  of  which  is  common  salt, 
NaCl.  This  is  a  combination  of  chlorine  with 
sodium,  and  is  believed  to  consist  of  one  atom  of 
each  combined  to  make  one  molecule  of  sodium 
chloride.  Chlorine  can  be  separated  from  common 
salt  by  treating  it  with  a  compound  known  as  man- 
ganese dioxide,  sulphuric  acid,  and  water.  The  ex- 
periment is  rather  complicated.  When  the  chlorine 
gas  is  separated,  it  is  seen  to  be  a  greenish-yellow 
color.  This  gives  it  its  name,  from  the  Greek, 
chloros,  which  means  "  green " ;  and  its  odor,  in 
small  quantities,  resembles  that  of  seaweed.  In 
large  quantities  it  is  dangerous  to  inhale  it,  as  it 
causes  a  severe  inflammation.  It  is  more  than 
twice  as  heavy  as  air,  and  when  it  is  put  under 
pressure  about  five  times  that  of  the  atmosphere 
(80  pounds  to  a  square  inch),  it  condenses  to  a 
yellow  liquid. 

The  chief  use  of  chlorine  in  manufactures  is  as 
a  bleaching  agent.  It  is  to  chlorine  that  chloride 
of  lime  owes  its  power  as  a  bleacher.  It  is  also 
used  as  a  disinfectant  and  deodorizer  and  as  a  solv- 
ent of  gold.  Gold  ores  are  crushed,  and  the  chlo- 
rine unites  with  the  metal  to  form  gold  chloride 
(AuCl3),  from  which  the  chlorine  may  be  sepa- 


ABOUT    COMMONER   ELEMENTS      111 

rated  by  the  use  of  other  chemicals.  Its  action 
in  disinfecting  and  bleaching  depends  upon  the  fact 
that  chlorine  readily  combines  with  hydrogen,  and 
thus  separates  it  from  water  (H2O),  leaving  the 
oxygen  free.  The  oxygen,  when  just  set  free,  is 
believed  to  be  separated  into  its  atoms,  and  these 
atoms  thus  set  free,  and  called  "  nascent,"  combine 
with  other  substances,  even  when  the  same  atoms 
in  a  molecule  of  oxygen  would  not  have  this 
power.  When  combined  with  hydrogen,  the  chlo- 
rine forms  hydrogen  chloride,  or  hydrochloric  acid. 
It  is  formed  by  bringing  together  equal  volumes  of 
the  gases,  hydrogen,  and  chlorine.  These,  when  ex- 
posed to  the  light,  at  once  join,  making  the  same 
volume  of  hydrochloric  acid  gas.  If  the  light  be 
strong,  the  two  gases  unite  with  a  violent  explo- 
sion. The  symbol  for  hydrochloric  acid  is  HC1. 
As  already  stated,  it  is  also  called  muriatic  acid. 

There  is  a  process  for  obtaining  chlorine  from 
hydrochloric  acid  gas,  by  heating  it  with  oxygen, 
whereupon  the  oxygen  unites  with  the  hydrogen 
to  form  water,  leaving  the  chlorine  free.  Another 
method  is  to  decompose  common  salt  by  electricity, 
much  as  we  have  seen  that  water  can  be  separated 
into  its  gases  by  the  same  agent. 


112      ABOUT    COMMONER    ELEMENTS 

Since  it  is  so  much  heavier  than  air,  chlorine 
gas  may  be  allowed  to  flow  into  a  jar  of  air,  where- 
upon it  collects  at  the  bottom  and  gradually  forces 
the  air  up  and  out. 

Just  as  charcoal  and  iron  may  be  burned  in 
pure  oxygen,  certain  elements  will  burn  in  chlorine. 
Thus  antimony  and  arsenic  sprinkled  into  it  com- 
bine with  a  flame.  Phosphorus  it  first  melts  and 
then  burns.  Several  metals,  when  heated,  will  con- 
tinue to  burn  in  chlorine,  but  chlorine  does  not 
combine  with  carbon  directly,  and  therefore  a  piece 
of  glowing  charcoal  thrust  into  it  is  put  out.  The 
atomic  weight  of  chlorine  is  35.18. 

BROMINE 

Bromine  (Br)  occurs  in  nature  in  common  with 
chlorine,  and  is  likewise  found  combined  with 
sodium.  Its  atomic  weight  is  80.*  Bromine  is  pre- 
pared in  two  ways.  It  is  extracted  from  potassium 
bromide  by  using  sulphuric  acid  and  manganese 
dioxide;  or  by  passing  chlorine  into  a  solution  of 
potassium  bromide,  the  bromine  is  replaced  by  the 
chlorine  and  so  set  free.  Electricity  also  may  be 
used  to  separate  bromine  from  bromides  that  are 

*  For  correct  atomic  weights,  see  the  tables.  In  the  text 
round  numbers  are  often  used. 


ABOUT    COMMONER    ELEMENTS      113 

soluble.  It  is  a  heavy,  dark  red  liquid,  easily 
changed  to  a  brownish  red  vapor.  It  gets  its  name 
from  its  bad  smell,  bromos,  in  Greek,  meaning  a 
stench.  It  acts  much  like  chlorine,  combining  with 
many  elements  very  readily.  It  is  somewhat 
weaker  than  chlorine,  and  chlorine  brought  into 
contact  with  its  compounds  will  often  replace  it. 
It  was  discovered  in  1826,  in  sea  water,  by  a  chem- 
ist named  Balard.  It  is  very  volatile,  easily  giving 
off  fumes.  It  has  a  destructive  effect  on  the  skin, 
burning  it  terribly. 

It  is  principally  used  as  a  disinfectant  and  in 
preparing  dyes.  It  is  a  bleaching  agent,  like  chlo- 
rine, though  weaker.  In  medicine,  potassium  bro- 
mide, or  bromide  of  potassium  (KBr),  is  used  as 
a  sedative.  The  bromide  of  silver  is  of  great  im- 
portance in  photography,  being  used  to  make  print- 
ing papers  and  sensitive  emulsions. 

IODINE 

Iodine  (I),  the  atomic  weight  of  which  is  125.9, 
is  a  solid,  dark  bluish-black,  with  a  metallic  lustre. 
When  heated  slightly  it  is  changed  to  a  beautiful 
violet  gas,  and  from  this  gets  its  name,  the  Greek 
name  meaning  violet.  It  is  less  irritating  in  vapor 
than  chlorine,  and  has  feebler  bleaching  powers. 


114      ABOUT    COMMONER   ELEMENTS 

Like  chlorine  and  bromine,  iodine  is  used  as  a  deo- 
dorizer and  disinfectant.  It  is  prepared  in  much 
the  same  way  as  these  two  elements.  Its  vapor  is 
nearly  nine  times  heavier  than  air.  It  dissolves 
slightly  in  water  and  freely  in  alcohol,  ether,  and 
several  other  solutions.  It  combines  so  readily 
with  phosphorus  that  when  brought  together  the 
phosphorus  burns.  Iodides,  as  will  be  seen,  are  in 
their  general  action  much  like  the  chlorides  and 
bromides.  It  is  much  used  in  medicine,  to  prevent 
the  spread  of  eruptions,  to  reduce  swellings,  and  to 
dress  wounds. 

FLUORINE 

The  remaining  member  of  the  family  is  fluorine 
(F).  Its  atomic  weight  is  19.  It  is  a  greenish- 
colored  gas,  with  a  strong,  irritating  odor,  and  read- 
fly  attacks  most  substances,  that  is,  forms  new 
compounds  with  other  elements.  It  is  of  recent 
discovery,  and  only  important  because  of  one  or 
two  of  its  compounds.  Most  important  of  these 
is  hydrofluoric  acid,  HF.  This  is  a  very  active, 
colorless  gas,  valuable  in  the  arts  because  it  readily 
dissolves,  or  corrodes,  glass,  and  so  may  be  used 
for  etching  patterns  on  it.  This  is  done  by  cover- 
ing glass  with  a  thin  coating  of  wax,  then  remov- 


ABOUT    COMMONER    ELEMENTS      115 

ing  the  wax  in  a  pattern,  and  exposing  the  whole  to 
the  vapor  of  the  hydrofluoric  acid.  These  fumes 
eat  into  the  exposed  glass,  but  do  not  attack  the 
wax.  Warm  water  then  will  remove  the  wax. 

Its  density  is  1.265,  very  slightly  greater  than 
air.  Its  activity  is  shown  by  the  fact  that  hydro- 
gen, bromine,  iodine,  sulphur,  phosphorus,  carbon, 
silicon,  and  boron  all  take  fire  when  immersed  in 
it.  Most  metals  form  fluorides  with  it.  It  does 
not  unite  with  oxygen.  But  fluorine  is  the  only 
element  that  does  not  combine  with  oxygen. 

This  completes  the  account  of  the  fluorine  group, 
and  the  close  relation  between  its  members  is  read- 
ily seen.  Thus,  all  form  colored  vapors.  They 
combine  strongly  with  many  substances,  fluorine 
having  a  stronger  affinity,  when  it  combines  at  all, 
while  chlorine,  bromine,  iodine,  follow  in  that 
order.  All  of  them  combine  in  single  atoms,  and 
when  combined  with  other  elements,  compounds 
made  in  the  same  way  resemble  one  another  in 
properties.  These  properties  seem  to  depend  in 
some  way  upon  the  atomic  weights  of  these  ele- 
ments, as  the  properties  change  in  the  same  order 
with  the  increase  of  atomic  weights,  as  will  be  seen 
later. 


116      ABOUT    COMMONEB    ELEMENTS 

It  will  be  found  that  the  same  thing  is  true  in. 
regard  to  other  chemicals  having  a  similar  family 
relation.  Thus,  if  we  know  the  atomic  weight  of 
an  element,  we  can,  to  some  extent,  foretell  its 
properties,  though  the  reason  for  this  is  not  yet 
known.  Putting  down  in  order  the  weights  of 
fluorine,  chlorine,  bromine,  and  iodine,  we  shall 
have  19,  35.5,  80,  and  127.  Koughly,  these  num- 
bers show  a  regular  progression  in  the  order  of  the 
strength  of  their  action. 

The  second  family  is  the  sulphur  family,  con- 
sisting of  the  very  common  element,  sulphur,  and 
the  rarer  elements  selenium  and  tellurium,  and  in 
connection  with  them  oxygen  is  often  grouped  since 
it  somewhat  resembles  them.  Selenium  and  tellu- 
rium are  exceedingly  rare,  but  form  compounds — 
selenides  and  tellurides — resembling  those  of  sul- 
phur. 

THE  SULPHUR  GROUP 

There  are  four  elements  ranged  under  this  head, 
and  one  of  them  is  oxygen,  concerning  which  much 
has  been  said  already,  and  of  the  other  three  the 
only  important  one  is  sulphur,  the  two  others  being 
very  rare  elements  of  very  little  importance  except 
to  professional  chemists,  and  having  no  characters 


From  Stereograph,  Copyright,  by  Underwood  *  Undenoood,  New  York. 

SULPHUE  SPRINGS. 


ABOUT    COMMONER   ELEMENTS      117 

we  need  remember,  except  that  their  compounds, 
in  general,  are  not  very  unlike  those  of  sulphur. 

SULPHUR 

Sulphur  itself,  however,  is  exceedingly  impor- 
tant. In  the  first  place,  it  has  been  known  since 
the  very  earliest  times,  probably  because  it  occurs 
in  large  quantities  in  its  pure  state  in  volcanic 
regions;  secondly,  because  it  is  so  peculiar  in  ap- 
pearance and  has  such  striking  properties.  It  is 
also  found  in  a  pure  state,  or  nearly  so,  near  beds 
of  gypsum,  which  itself  is  a  sulphur  compound. 
A  great  deal  of  it,  nowadays,  comes  from  Sicily 
and  from  South  America.  It  exists  among  differ- 
ent rocks  in  its  various  compounds,  and  is  also 
found  in  many  articles  of  daily  food,  being  impor- 
tant especially  in  onions,  horseradish,  garlic,  and 
in  the  yolks  of  eggs.  It  enters  into  the  composition 
of  animal  bodies,  of  which  it  forms  a  most  impor- 
tant constituent.  In  the  human  body  there  is  a 
little  more  than  a  quarter  of  a  pound  of  sulphur 
in  various  forms.  It  is  produced,  when  not  found 
pure,  by  heating  what  is  known  as  its  "  ore,"  which 
is  purified  and  the  sulphur  melted  from  it,  or 
washed  from  it  by  hot  water  or  steam.  After  it  is 


118      ABOUT    COMMONER    ELEMENTS 

liquefied,  still  further  heating  makes  it  a  vapor, 
and  this  vapor,  when  condensed  on  a  cool  surface, 
takes  on  a  powdery  form. 

In  its  commonest  form  it  is  yellow,  brittle,  and 
often  in  crystals.  It  weighs  about  twice  as  much 
as  water.  When  heated,  it  at  first  melts  into  a 
light  amber-colored  liquid,  then  gradually  darkens 


KILN  FOB  EXTRACTING  SULPHUE  FORM  CRUDE  ORE 
It  is  shown  as  a  vertical  section  (right)   and  in  operation  (left). 

and  thickens  into  a  very  sticky,  dense  liquid.  Fur- 
ther heating  causes  it  to  thin  again,  finally  to  boil 
and  change  to  a  vapor.  If  it  catches  fire,  it  burns 
with  a  pale  blue  flame.  It  combines  readily  with 
hydrogen,  carbon,  chlorine,  and  most  metals,  mak- 
ing compounds  of  two  elements,  or  "sulphides." 
Chemists  place  it  among  the  non-metals,  and  find 
that  it  exists  in  a  number  of  forms,  or  is  allotropic. 


ABOUT    COMMONER    ELEMENTS      119 

With  lead  it  forms  the  lead  sulphide,  "galena"; 
with  mercury,  it  forms  the  sulphide  "  cinnabar." 
Both  of  these  ores  are  easily  freed  from  sulphur, 


APPARATUS  FOB  PUEIFYING  SULPHUR 

The  crude  sulphur  is  melted  in  B,  and  flows  into  the  iron 
cylinder,  A.  Here  it  is  heated,  and  the  vapors  pass  into  the 
large  brick  chamber,  provided  with  a  tap,  C,  from  which  the 
liquid  sulphur  may  be  withdrawn. 

giving  the  lead  and  mercury  pure.  Cinnabar  is 
useful  to  artists,  being  the  pigment  vermilion, 
though  this  color  is  the  very  pure  sulphide  arti- 
ficially produced. 


120      ABOUT    COMMONER    ELEMENTS 

A  mass  of  sulphur,  when  rubbed,  becomes  elec- 
trified negatively,  and  a  ball  of  sulphur  mounted 
on  an  axis  so  as  to  be  revolved  against  a  rubber, 
made  the  first  electric  machine. 

There  are  at  least  six  different  sorts  of  sulphur 
known  to  chemists,  though  we  shall  not  try  to  de- 
scribe them  very  accurately. 

1.  In  crystals  known  as  orthorhombic ;  that  is 
to  say,  crystals  having  three  unequal  axes  crossing 
at  right  angles.     This  seems  to  be  the  primary  form 
of  the  sulphur  crystals,  for  other  forms,  left  to 
themselves,  gradually  change  back  to  this  one. 

This  form  of  sulphur  is  soluble  in  ether,  benzine, 
and  some  other  chemicals,  but  not  in  water. 

2.  When  sulphur  is  first  melted  and  allowed  to 
cool,  it  forms  what  are  called  monoclinic  crystals, 
or  crystals  with  three  unequal  axes,  two  crossing 
obliquely,  and  the  third  at  right  angles  to  the  plane 
of  these  two.     If  this  form  of  sulphur  be  left  to 
itself,  it  will,  as  has  been  said,  gradually  change 
to  the  first  form.     This  is  soluble  in  alcohol  and  in 
ether,  and  in  some  other  liquids,  but  not  in  water. 

3.  A  soft,  formless,  whitish  form  of  sulphur,  be- 
lieved to  contain  some  hydrogen.     This,  when  left 


ABOUT    COMMONER   ELEMENTS      121 

to  itself,  gradually  hardens  and  changes  to  the  first 
form. 

4.  An  insoluble  form  of  sulphur,  that  is  plastic, 
or  may  be  moulded. 

5.  A  form  called  "  amorphous  "  or  formless,  yel- 
low, and  insoluble. 

6.  A  form  known  as  "  colloidal." 

These  last  three  forms  are  distinguished  from  one 
another  by  their  differences  in  solubility,  and  so 
forth.  The  different  forms  also  do  not  agree  in 
specific  gravity  and  some  other  qualities. 

As  ordinarily  sold,  sulphur  comes  in  long  sticks, 
or  rolls,  known  as  brimstone,  or  rolled  sulphur. 
These,  crushed,  become  ordinary  sulphur.  Very 
finely  powdered  sulphur  is  known  as  flowers  of  sul- 
phur. Sulphur  is  very  useful  medically. 

Its  symbol  is  S;  its  atomic  weight  31.82.  The 
importance  of  knowing  its  different  forms  depends 
upon  the  fact  that  these  help  us  to  make  guesses 
at  the  arrangement  of  its  atoms  in  making  up  the 
molecules.  Since  the  material  composition,  or 
make-up,  of  an  element  is  always  the  same,  when 
we  see  that  certain  changes  in  its  condition  cause 
it  to  assume,  as  in  the  case  of  sulphur,  six  varying 


122     ABOUT    COMMONER   ELEMENTS 

forms,  we  can  only  explain  these  by  supposing  that 
the  little  atoms  forming  its  molecules  are  arranged 
in  some  different  manner  or  relation.  And  this 
becomes  very  important  when  we  study  the  com- 
pounds of  the  various  elements,  especially  those  of 
carbon.  Many  of  its  compounds  can  only  be  under- 
stood by  supposing  that  the  same  atoms  are  ar- 
ranged in  different  ways  in  their  make-up. 

The  important  compounds  of  sulphur  are  many. 
Thus,  with  hydrogen  it  forms  H2S,  or  sulphuretted 
hydrogen.  Its  chemical  name  is  hydrogen  sul- 
phide. It  is  a  gas,  occurring  in  the  waters  of  sul- 
phur springs  and  in  volcanic  gases.  It  is  one  of  the 
impurities  of  illuminating  gas,  and  may  be  found  in 
the  air  near  sewers  and  cesspools,  being  sometimes 
formed  by  the  decay  of  organic  substances  which 
contain  sulphur;  thus  it  is  formed  when  eggs  de- 
cay— and  causes  their  bad  odor.  It  is  colorless  and 
poisonous.  It  is  useful  in  the  chemical  laboratory 
as  a  "reducer,"  that  is  to  say,  as  a  means  of  ex- 
tracting oxygen  from  compounds.  If  a  house  be 
heated  with  coal,  hydrogen  sulphide  in  the  air  will 
often  cause  silverware  to  tarnish,  the  tarnishing 
being  due  to  the  formation  of  silver  sulphide. 
A  similar  chemical  action  is  caused  upon  silver 


ABOUT    COMMONER    ELEMENTS      123 

spoons  when  these  are  brought  into  contact  with 
mustard  or  the  yolks  of  eggs.  White-lead  paint, 
whether  upon  the  walls  of  a  house  or  on  oil-paint- 
ings, is  also  tarnished  by  this  gas,  becoming  greyer. 
Hydrogen  sulphide  is  often  useful  in  chemical  anal- 
ysis, as  when  sulphides  of  metals  are  formed  by  its 
use,  they  may  be  recognized  by  their  different 
colors. 

SULPHUR  DIOXIDE 

Sulphur  dioxide  is  the  common  compound  of  sul- 
phur with  oxygen,  which  is  important  particularly 
in  the  manufacture  of  sulphuric  acid.  Sulphur 
dioxide  is  also  used  for  preserving  food,  for  fumi- 
gation, in  tanning,  and  in  the  refining  of  sugar, 
and  in  a  dozen  other  ways. 

SULPHURIC  ACID 

But  the  most  important  of  the  sulphur  com- 
pounds is  sulphuric  acid.  The  formula  for  this  is 
H2SO4.  In  an  article  on  the  part  played  by  chem- 
istry in  human  progress,  Professor  Austin,  of  Rut- 
gers College,  says :  "  If  one  were  to  ask  how  the 
state  of  civilization  of  a  country  should  be  judged, 
one  would  probably  be  told  how  many  churches 
there  were,  attention  would  be  drawn  to  the  volume 


124      ABOUT    COMMONER   ELEMENTS 

of  business  done,  fine  hospitals,  the  excellence  of 
the  police,"  and  so  on.  "  But,"  he  says,  "  the  chem- 
ist would  simply  determine  the  amount  of  sul- 
phuric acid  used,  directly  or  indirectly,"  for  he  de- 
clares that  nearly  everything  used  by  civilized 
people  requires  in  its  making  this  acid. 

The  uses  of  this  acid  are  beyond  enumeration, 
and  it  has  been  well  said  that  the  health  and  pros- 
perity of  a  nation  can  be  measured  by  the  amount 
of  it  in  use.  A  large  part  goes  to  the  making  of  fer- 
tilizers. It  is  used  in  making  all  other  mineral 
acids,  and  many  others  besides.  It  is  necessary  in 
one  process  for  making  sodium  carbonate,  a  com- 
pound that  enters  into  all  soap  and  glass.  It  is 
used  in  the  manufacture  of  alum,  nitro-glycerine, 
glucose,  phosphorus,  dye-stuffs,  in  bleaching,  in 
electric  batteries,  refining  and  metal  working,  and, 
in  short,  is  the  commonest  of  the  acids  used  in  the 
arts.  In  fact,  there  are  very  few  of  our  indus- 
tries which  do  not  depend  more  or  less  upon  sul- 
phur or  some  of  its  compounds,  to  say  nothing  of 
its  direct  uses,  such  as  in  making  gunpowder  and 
fireworks,  in  the  making  of 'matches  and  in  the 
hardening  of  crude  rubber.  We  are  so  used  to 
what  we  know  as  hard  and  soft  rubber  that  we  do 


ABOUT    COMMONER    ELEMENTS      125 

not  realize  how  recent  is  the  discovery  of  a  means 
for  making  this  useful  substance.  It  was  only 
after  years  of  study,  and  to  some  extent  by  happy 
accident,  that  Charles  Goodyear  discovered  the 
means  of  hardening  rubber  by  adding  sulphur  to 
it — that  is,  of  "  vulcanizing  "  it. 

Sulphuric  acid  is  what  is  known  as  di-basic,  that 
is,  it  forms  two  classes  of  salts,  the  normal  and  the 
acid  salts.  The  sulphates  thus  formed,  either  natu- 
rally or  artificially,  are  most  important.  The  sul- 
phate of  calcium  is  gypsum,  known  in  various  forms 
as  plaster  of  Paris  and  alabaster.  Zinc  sulphate 
makes  white  vitriol,  while  copper  and  iron  form 
respectively  blue  and  green  vitriol.  Sodium  sul- 
phate is  the  well-known  Glaubers  salt.  Magnesium 
sulphate  is  Epsom  salts.  Sodium  thio-sulphate  is, 
as  has  already  been  explained,  the  correct  name  for 
what  we  call  hypo-sulphite  of  soda,  the  fixing  salt  of 
photographers.  With  carbon,  sulphur  forms  carbon 
di-sulphide,  a  liquid  that  is  very  useful  from  its 
property  of  dissolving  rubber,  various  gums  and 
fats,  and  so  on.  Rubber  dissolved  with  it  makes 

rubber  cement. 

SELENIUM 

Selenium,    whose    symbol    is    Se,    and    atomic 


126      ABOUT    COMMONER    ELEMENTS 

weight  78.6,  is  a  non-metallic  element  occurring  in 
two  forms  (1),  a  red  powder,  and  (2)  a  dark  glassy 
mass  sometimes  crystajlized.  This  element  was 
discovered  by  Berzelius,  in  1817,  and  has  no  other 
interest  for  the  general  reader  than  a  resemblance 
in  its  compounds  to  the  similar  compounds  of  sul- 
phur. Selenium  is  important  to  the  electrician  be- 
cause its  resistance  to  electricity  varies  with  the 
amount  of  light.  This  property  is  used  in  the 
"  photophone,"  where  a  ray  of  light  transmits 
speech  by  aid  of  a  selenium  cell;  and  in  other 
ways. 

TELLURIUM 

Tellurium,  symbol  Te,  with  an  atomic  weight 
of  127.6,  was  discovered  in  1782  by  von  Reichen- 
stein.  It  is  a  silver-white  metal,  brittle,  and  also 
forms  compounds  generally  resembling  those  of  the 
other  elements  of  this  group. 

Simply  to  complete  the  group,  we  name  here  also 
oxygen,  the  gaseous  non-metallic  element,  whose 
atomic  weight  is  15.88.  Its  properties  have  already 
been  discussed.  But  while  considering  it  in  this 
place,  it  may  be  well  to  say  that  it  is  sometimes 
taken  to  have  an  atomic  weight  of  exactly  16.  You 
will  remember  that  the  meaning  of  atomic  weight 


ABOUT    COMMONER   ELEMENTS      127 

is  simply  weight  compared  with  an  atom  of  hydro- 
gen. Now  if  hydrogen  atoms  be  taken  to  weigh 
1,  the  oxygen  atoms  must  be  taken  to  weigh  15.88. 
But  if,  on  the  contrary,  we  choose  oxygen  as  being 
the  measure  and  call  it  16  exactly,  then  a  very 
slight  change  will  be  necessary  to  adjust  all  other 
atomic  weights  to  this  new  scale.  Hydrogen,  in- 
stead of  being  1,  will  now  become  1.008,  and  as  we 
go  through  the  list  of  elements  giving  the  atomic 
weights  the  slightly  larger  values  that  is  made  nec- 
essary by  considering  oxygen  to  weigh  16  instead 
of  15.88,  we  shall  find  that  a  large  number  of  ele- 
ments change  their  values  from  fractions  to  whole 
numbers.  Among  these  are  arsenic,  boron,  carbon, 
fluorine,  manganese,  mercury,  radium,  and  tin.  As 
it  is  more  convenient  to  work  sums  in  the  whole 
numbers,  chemists  are  now  beginning  to  adopt  these 
new  values,  merely  as  a  matter  of  convenience; 
and  even  where  a  table  is  given  showing  one  set 
of  values  ( with  hydrogen  1 )  other  values  with  oxy- 
gen equals  16  are  usually  written  after  them.  The 
change  is  very  slight,  and  very  convenient.  The 
table  of  elements  in  the  last  chapter  of  this  book 
gives  both  atomic  weights. 


OF  THE 

UNIVERSITY 

OF 


CHAPTER  IX 

THE  METALLIC  ELEMENTS 

FOR  ages  chemists  believed  that  there  was  a  sharp 
division  between  the  classes,  metals  and  non-metals. 
Those  elements  which  were  opaque,  shiny,  heavy, 
hard,  and  malleable,  were  called  metals;  those  ele- 
ments which  did  not  have  these  properties,  the  non- 
metals.  Some  elements,  such  as  antimony  and  bis- 
muth in  certain  ways  appeared  to  be  metals  and 
acted  like  them;  in  other  ways  they  seemed  to  be- 
long to  the  non-metal  class.  They  are  therefore 
still  referred  to  as  "  metalloids,"  or  metal-like  ele- 
ments, though  strictly  speaking,  they  are  metals. 

Still,  though  the  definition  of  metal  and  non- 
metal  has  now  been  changed  to  express  chemical 
rather  than  physical  qualities,  yet  the  distinction 
is  a  useful  one,  and  need  not  cause  confusion.  In 
general,  therefore,  we  may  say  of  metals  that  they 
are  shiny,  and,  when  pure,  that  they  do  not  (ex- 
cepting the  thinnest  silver  and  gold  foils)  trans- 
mit light.  Many  metals  are  white,  such  as  silver, 

129 


130          THE    METALLIC    ELEMENTS 

sodium,  aluminum,  mercury,  magnesium,  and  iron. 
Iron,  of  course,  soon  takes  on  a  red  surface  if 
exposed  to  the  air,  because  oxide  of  iron  is  red. 
Bismuth  is  reddish  white ;  gold  is  yellow ;  copper  is 
the  only  metal  element  that  is  red.  The  quality 
of  being  malleable  and  ductile  belongs  to  most 
metals,  though  in  different  degrees.  Hardness 
varies  very  greatly,  from  the  liquid  mercury  or 
such  soft  elements  as  sodium  and  lead  which  are 
readily  dented  or  cut,  to  such  hard  metals  as  irid- 
ium,  which  is  as  hard  as  steel,  or  harder.  The 
specific  gravity  of  metals,  or  their  weight  compared 
to  water,  also  varies  widely. 

In  the  last  chapter,  among  the  tables,  we  give 
the  physical  qualities  of  the  best  known  metals. 

METALS 

It  is  characteristic  of  metals  that  they  are  spe- 
cially good  conductors  of  electricity  and  of  heat. 
Chemically,  they  unite  with  oxygen  to  form  oxides, 
and  with  hydrogen  and  oxygen  they  make  bases, 
whereas  the  non-metallic  elements  form  compounds 
that  produce  acids. 

In  nature  metals  occur  but  seldom  in  a  pure 
form,  the  only  two  at  all  commonly  so  found  being 


THE    METALLIC    ELEMENTS          131 

gold  and  copper.  Gold  is  found  pure  usually  in 
very  small  amounts,  in  mere  grains,  though  excep- 
tionally now  and  then  immense  nuggets  have  been 
found  in  certain  localities.  Copper,  along  our 
Great  Lakes,  occurs  sometimes  in  large  masses,  al- 
most pure. 

But,  for  the  most  part,  owing  to  the  fact  that 
the  metals  combine  readily  with  other  elements, 
they  are  found  in  their  ores,  or  compounds,  most 
often  with  one  of  the  four  common  elements,  car- 
bon, hydrogen,  oxygen,  and  sulphur.  In  their  ores, 
silver,  tin,  iron,  and  lead,  are  not  only  plentiful, 
but  are  found  in  many  districts  throughout  the 
world.  The  pure  metals  can  be  obtained  from  the 
ores  by  various  methods,  the  treatment  including 
especially  the  use  of  heat,  electricity,  and  a  wide 
variety  of  chemical  processes. 

The  mixtures  of  metals,  whether  chemically 
united  or  not,  are  usually  called  "  alloys,"  except 
in  the  case  of  mercury.  Mercury  mixtures,  which 
are  in  consistency  somewhat  between  the  liquid 
state  of  mercury  and  the  solid  state  of  the  metal 
mixed  with  it,  are  called  "  amalgams." 

Since  alloys  may  be  made  without  true  chemical 
union,  they  differ  in  composition  in  every  degree. 


132         THE    METALLIC    ELEMENTS 

The  more  important  of  them  will  be  found  men- 
tioned under  the  metals  of  which  they  consist. 
They  are  mixed  from  the  melted  metals,  and  vary 
much  from  their  constituents,  as  in  color,  hardness, 
conducting  power  for  heat  or  electricity,  and  espe- 
cially ease  of  melting.  Sometimes  an  alloy  will 
melt  at  a  far  lower  degree  of  heat  than  any  of  its 
constituents.  Many  metals  will  mix  readily  and  in 
widely  varying  quantities,  while  others  do  not  unite 
readily. 

The  properties  of  metals  often  vary  widely,  ac- 
cording to  how  the  metals  have  been  prepared. 

GOLD 

In  discussing  the  elements,  we  shall  begin  with 
gold.  This  has  been  known  to  mankind  since  the 
earliest  times,  and  has  been  highly  valued  primarily 
because  of  its  great  beauty.  It  has  an  attractive 
color,  a  bright  yellow  that  is  unchangeable  under 
all  ordinary  treatment.  It  is  so  very  malleable 
and  ductile  that  it  lends  itself  readily  to  use  for 
ornaments  of  every  kind.  Thus  it  can  be  beaten 
into  flat  plates,  or  gold-leaf,  so  thin  that  the  small- 
est quantity  may  be  extended  to  cover  broad  sur- 
faces. It  will  draw  into  wire  of  the  finest  thinness 


THE    METALLIC    ELEMENTS          133 

without  breaking,  and  in  these  forms,  leaf  and  wire, 
may  be  so  disposed  as  to  make  a  great  show  with  a 
very  small  amount  of  material.  In  the  earliest 
times  the  fact  that  it  was  valued  by  every  one  gave 
it  an  exchange  power  that  soon  made  it  perform  the 
offices  of  money.  Being  small  in  bulk,  ready  to  use 
with  little  treatment,  and  adaptable  to  so  many 
uses,  all  nations  and  all  individuals  were  glad  to 
get  it,  and  it  thus  offered  a  convenient  means  of 
keeping  wealth  on  hand.  As  knowledge  of  the  arts 
advanced,  it  became  usual  to  mix  gold  with  a  pro- 
portion of  copper  or  silver,  to  prevent  its  wearing 
away  so  easily,  and  this  led  to  the  adoption  of  a 
standard  expressing  the  proportion  of  pure  gold 
in  the  mixture.  The  ordinary  means  of  measuring 
this  is  by  carats,  twenty-four  carats  being  consid- 
ered the  fineness  of  pure  gold.  If  two  parts  in 
twenty-four  are  made  up  of  another  metal,  the 
gold  is  considered  to  be  twenty-two  carats  fine. 
Jewelers'  gold,  for  the  making  of  ornaments,  ranks 
thus  from  twelve  to  twenty-two  carats,  anything 
lower  than  twelve  containing  too  little  gold  to  be 
acceptable,  and  anything  higher  than  twenty-two 
wearing  away  too  readily. 

Chemically,  the  symbol  for  gold  is  derived  from 


134          THE    METALLIC    ELEMENTS 

the  Latin  word  aurum,  being  An.  Its  atomic 
weight  is  197,  its  specific  gravity  19 — making  it  by 
far  the  heaviest  of  the  commoner  metals,  only  plati- 
num being  heavier.  Gold  is  less  easily  melted  than 
silver,  m0re  so  than  copper.  Pure  gold  is  harder 
than  lead,  but  softer  than  silver.  A  single  grain 
of  gold  can  be  beaten  out  into  a  leaf  covering  an 
area  of  eighty  square  inches,  and  the  metal  can 
be  drawn  into  a  wire  two  hundred  thousand  of 
which,  laid  side  by  side,  would  cover  but  an  inch. 
To  make  this  finest  wire,  however,  special  methods 
are  used,  the  gold  being  drawn  out  in  a  wire  sur- 
rounded by  platinum,  after  which  the  platinum 
is  dissolved  off  by  nitric  acid. 

Gold  has  been  so  greatly  valued  because  of  its 
many  useful  properties.  It  readily  mixes  with 
other  metals,  and  is  made  into  alloys,  giving  com- 
pounds widely  different  in  their  properties  and 
adaptable  to  many  uses.  Gold  resists  the  action 
of  nearly  all  acids,  being  soluble  only  in  a  mix- 
ture of  nitric  acid  and  hydrochloric,  one  of  the 
first,  and  three  or  four  parts  of  the  latter.  This 
mixed  acid,  owing  to  its  power  to  dissolve  gold, 
received  the  name  aqua  regia.  Other  solvents  will 
dissolve  it,  but  only  when  the  gold  is  in  a  very 


THE    METALLIC    ELEMENTS          135 

fine  state.  Its  use  may  be  generally  stated  under 
a  few  main  classes.  Immense  quantities  are  used 
in  coinage;  in  jewelry,  especially  in  plating  on 
other  metals ;  in  the  coloring  of  china  and  of  glass, 
and  of  artificial  gems;  it  is  used  in  gilding,  as  on 
picture-frames,  books,  signs,  and  ornaments,  and 
can  readily  be  deposited  from  the  electric  bath. 
Gold  is  widely  used  in  photography,  though  in  small 
quantities,  being  deposited  in  a  fine  state  upon  pho- 
tographic prints  in  toning  them.  A  by  no  means 
small  quantity  is  used  by  dentists,  and  a  few  com- 
pounds of  gold  are  employed  in  medicine.  Gold,  to 
unknown  amounts,  is  hoarded  by  individuals  and 
by  States,  especially  in  the  East,  and  is  kept  on 
deposit  in  all  civilized  countries  to  insure  the  re- 
demption of  other  forms  of  money.  Chemically, 
gold  compounds  are  useful  mainly  in  coloring,  or 
gilding  pottery  and  in  the  preparation  of  stained 
glass. 

SILVER 

The  metal,  silver,  is  white,  harder  than  gold, 
softer  than  copper,  and  especially  notable  for  its 
brilliancy  when  polished,  though  less  so  than  gold. 
Silver  also  is  ductile  and  malleable,  readily  con- 
verted into  wire  or  thin  leaves.  In  weight  it  has 


136          THE    METALLIC    ELEMENTS 

a  specific  gravity  of  10.5,  being  heavier  than  cop- 
per, lighter  than  lead  or  gold.  It  is  the  best  con- 
ductor of  heat,  except  gold,  of  any  of  the  metals, 
and  almost  the  best  conductor  of  electricity.  It 
has  been  considered  less  valuable  than  gold,  simply 
because  it  is  more  plentiful  and  because,  owing  to 
its  great  affinity  for  sulphur,  it  tarnishes  readily 
in  the  air,  taking  on  a  thin  coating  of  the  black 
compound,  sulphide  of  sulphur.  Advantage  is 
taken  of  this  to  darken  silver  by  the  sulphide,  when 
it  goes  by  the  name  oxidized  silver.  For  use  in 
coins  and  jewelry,  silver  is  alloyed  with  copper, 
coined  silver  being  90%ooo  pure  silver  in  the  United 
States,  and  92%ooo  in  England,  the  latter  being 
"  sterling  silver." 

Silver  ores  are  very  widely  distributed,  and  are 
usually  compounds  with  carbon  and  sulphur,  the 
commonest  being  silver  sulphide.  Vast  quantities 
of  silver  are  produced  by  the  mines,  especially  in 
the  United  States. 

Another  common  compound  is  the  chloride  of  sil- 
ver, or  horn  silver.  A  very  large  part  of  the  silver 
is  found  in  combination  with  lead,  and  most  lead 
ores  contain  it  in  paying  quantities.  The  most  im- 
portant processes  in  silver  mining  are  those  used 


THE    METALLIC    ELEMENTS          137 

to  separate  lead  from  silver.  One  method  is  to  heat 
the  ore  that  contains  the  two  metals,  which  causes 
the  lead  to  crystallize  when  the  heated  solution  is 
allowed  to  cool.  Since  the  lead  crystallizes  earliest 
it  can  be  dipped  from  the  solution,  leaving  silver 
that  contains  only  a  small  amount  of  lead.  The 
solution  is  next,  while  heated,  exposed  to  a  blast 
of  air  and  flame.  This  causes  a  combination  of  the 
lead  with  oxygen,  and  the  blast  carries  off  the  lead 
oxide  thus  formed,  leaving  the  silver  pure. 

By  another  method  zinc  is  added  to  the  solution 
of  lead  and  silver,  combines  with  the  silver  to  form 
an  alloy,  and  then  as  the  solution  cools,  this  alloy, 
zinc  and  silver,  rises  to  the  top,  being  lighter  than 
the  lead,  and  may  be  skimmed  off.  A  small  por- 
tion of  lead  still  remains,  but  by  being  heated,  this 
melts  before  the  alloy  and  is  allowed  to  run  off.  A 
further  heating  of  the  zinc  and  silver  alloy  vapor- 
izes the  zinc  and  leaves  the  silver  pure. 

Of  the  compounds  of  silver  one  of  the  most  im- 
portant is  silver  nitrate  (AgNO3).  It  is  formed  by 
dissolving  silver  in  nitric  acid.  It  is  used  for  sen- 
sitizing photographic  paper,  for  making  indelible 
ink,  and  for  certain  dyes.  When  crystallized  and 
moulded  into  sticks,  it  is  known  as  lunar  caustic, 


138          THE    METALLIC    ELEMENTS 

and  used  for  cauterizing  wounds.  Although  silver 
nitrate  is  sensitive  to  light,  and  turns  dark  when 
exposed  to  it,  especially  if  accompanied  by  certain 
other  substances,  yet  it  is  usual  to  convert  silver 
nitrate  into  silver  bromide,  or  silver  chloride,  in 
making  photographic  plates,  since  these  com- 
pounds are  even  more  sensitive.  Silver  chloride 
is  prepared  from  silver  nitrate  by  adding  chlorine, 
either  as  hydrochloric  acid,  chloride  of  sodium,  or 
any  other  soluble  chloride.  It  is  believed  that  light 
so  affects  silver  chloride,  or  silver  bromide,  as  to 
separate  the  silver  into  a  pure  and  finely  divided 
state,  and  this  action  is  greatly  hastened  and  in- 
creased by  the  use  of  the  developer  in  photography. 
The  chemistry  of  photography  has  been  most 
exhaustively  studied,  and  the  result  has  been  the 
creation  of  an  endless  number  of  processes  for  mak- 
ing plates,  developing  them,  and  especially  in  de- 
vising methods  for  printing.  The  underlying  prin- 
ciples, however,  are,  in  the  main,  the  same  in  all 
the  silver  processes.  The  fact  that  silver  chloride 
is  soluble  in  a  solution  of  sodium  thio-sulphate,  or 
"  hypo,"  is  what  makes  it  possible  to  fix  photo- 
graphs, since  by  use  of  the  hypo  bath  the  silver 
compounds  that  have  been  converted  to  metallic 


THE    METALLIC    ELEMENTS          139 

silver  may  be  washed  out,  leaving  the  metallic  sil- 
ver unaffected. 

Silver  forms  alloys  with  mercury,  platinum,  zinc, 
gold,  copper,  and  these  alloys  are  employed  for 
various  purposes  in  the  arts. 

COPPER 

This  metal,  owing  to  the  fact  that  it  is  found  in 
ores  from  which  it  is  easily  separated  by  the  use  of 
heat  alone,  was  one  of  the  earliest  discoveries  of 
mankind,  and  seems  to  have  been  the  first  of  the 
metals  to  be  useful  in  the  making  of  tools  and 
weapons.  It  was  plentiful  in  many  parts  of  the 
world,  greatly  valued  as  an  ornament,  readily  made 
into  utensils  and  into  wire,  and  so  became  one  of 
the  earliest  means  of  civilization.  Besides,  copper 
was  very  early  found  to  be  changed  into  an  even 
more  valuable  substance  when  mixed  with  a  small 
portion  of  tin  or  other  metals.  Thus  it  came  about 
that  just  after  the  discovery  of  this  earliest  metal 
in  its  simpler  compounds,  mankind  entered  upon 
what  is  known  as  the  Copper  Age,  and,  later,  the 
Bronze  Age,  which  periods  in  development  followed 
upon  the  earliest  Stone  Age,  that  in  which  man's 
best  tools  and  weapons  were  made  of  polished  stone. 


140          THE    METALLIC    ELEMENTS 

Copper  is  red,  and  is  very  flexible,  though  not  in 
its  pure  form  elastic.  Its  specific  gravity  is  8.9, 
atomic  weight,  63.1.  Excepting  silver  and  gold,  it 
is  the  best  conductor  of  electricity.  Although  it 
tarnishes  slightly  in  air,  a  compound  is  thus  formed 
on  the  surface  which  protects  the  metal  from  fur- 
ther action.  It  is  readily  beaten  into  sheets  or 
drawn  into  wire.  When  copper  is  heated  and 
plunged  into  water,  it  becomes  not  stiffened,  but 
more  malleable.  Its  name  is  derived  from  tjhe 
Latin,  Cyprium  aes,  which  meant  Cyprium  brass. 
Later,  the  noun  was  dropped  and  the  adjective  be- 
came condensed  into  cuprum,  from  which  it  gets 
its  chemical  symbol,  Cu.  It  forms  two  valuable 
alloys  when  mixed  with  zinc  and  tin,  and  these 
alloys  have  been  of  enormous  use  in  the  world,  that 
known  as  bronze,  which  contains  copper,  zinc,  and 
tin,  long  taking  the  place  in  the  world's  history 
now  held  by  steel.  Even  after  the  discovery  of 
steel,  this  bronze  was  long  used  for  making  can- 
non, bells,  statues,  and  so  on.  At  the  present  day 
the  uses  of  copper  are  almost  innumerable.  We 
can  only  hint  at  their  general  classes.  Thus,  it  is 
used  in  constantly  increasing  quantities  in  tele- 
graphing and  telephoning,  both  of  which  require 


Copyright,  l>y  Vnderwootl  ,{•   Underwood,  New  York. 

DRILLING   COPPER  ONE  MILE  UNDERGROUND. 


THE    METALLIC    ELEMENTS          141 

copper  wire  in  their  circuits;  in  electric  lighting 
and  motors,  and  in  electric  railways.  Copper  is 
used  also  in  all  forms  of  printing,  for  the  making 
of  electrotypes  and  half-tone  plates.  It  is  of  end- 
less use  in  household  utensils,  for  sheathing  ships, 
for  coinage,  nearly  all  of  the  cheaper  coins  contain- 
ing large  parts  of  copper.  In  its  alloys,  the  list 
of  which  is  constantly  growing,  copper  enters  into 
jewelry,  all  brasswork,  all  substances  composed  of 
gun  metal,  phosphorus,  bronze,  aluminium  bronze, 
manganese  bronze,  all  anti-friction  metals,  and  so 
on.  Our  nickel  coins,  so  called,  are  three-fourths 
copper. 

The  compounds  of  copper  are  usually  very  pois- 
onous. There  are  two  main  classes  of  these,  known 
respectively  as  the  cuprous  and  cupric.  These  two 
salts  of  copper  are  distinguished  by  the  fact  that 
one  of  them  contains  one  half  as  much  copper  as 
the  other,  the  cuprous  salts  containing  the  most. 

An  important  compound  of  copper  is  the  copper 
sulphate,  CuSO4,  called  "blue  vitriol."  This  con- 
sists of  blue  crystals,  soluble  in  water,  and  the  solu- 
tion is  much  used  where  a  simple  compound  of 
copper  is  necessary  in  chemistry.  It  is  a  most  use- 
ful solution  in  electric  batteries.  Solutions  of  cop- 


142          THE    METALLIC    ELEMENTS 

per  are  also  used  in  spraying-mixtures  for  killing 
insects.  Pigments  derived  from  copper  are 
Scheele's  green,  Brunswick  green,  and  emerald 
green.  Dangerous  compounds  of  copper  may  form 
when  copper  articles  are  exposed  to  damp  air.  In 
moist  air,  copper  unites  with  oxygen  to  some  extent 
forming  copper  oxide,  which  unites  with  carbon 
dioxide  in  the  air,  forming  carbonate  of  copper,  a 
green  compound.  Vinegar  (acetic  acid)  will  form 
with  copper,  verdigris  (or  copper  acetate)  which  is 
a  poison.  Other  foods  also  may  act  to  form  poison- 
ous compounds,  so  copper  vessels  should  not  be 
used  to  hold  food  permanently.  They  should  be 
tinned,  nickeled,  or  otherwise  protected.  Owing 
to  the  poisonous  nature  of  copper  compounds,  thje 
use  of  copper  utensils  in  cookery  requires  that  they 
be  kept  clean  and  polished,  and  that  substances  pre- 
pared in  them  be  removed  as  soon  as  possible,  to 
prevent  the  vegetable  juices  from  acting  upon  the 
copper  surface. 

The  cuprous  oxide  (Cu2O)  is  a  bright  red  pow- 
der. It  imparts  a  splendid  ruby  red  color  to  glass, 
and  is  used  also  in  giving  color  to  pottery.  Thus 
it  will  be  seen  that  the  chief  use  of  these  copper 
compounds  is  as  coloring  matters,  or  as  poisons. 


CHAPTER   X 

METALLIC  ELEMENTS,  CONTINUED 

IRON 

AN  important  group  of  metals  is  formed  of  the 
three,  iron,  nickel,  and  cobalt.  The  two  latter  are 
seldom  found  separated.  Iron  is  the  most  familiar, 
and,  in  the  sense  of  being  the  most  useful,  may  be 
considered  the  most  valuable  of  all  metals. 
Though  known  since  very  early  times,  there  were 
long  ages  wherein  copper  and  bronze  played,  imper- 
fectly, the  part  that  iron  was  subsequently  to  fill. 
When  iron  was  discovered,  probably  by  the  acci- 
dent of  using  its  ores  for  the  building  of  fireplaces, 
it  began  soon  to  take  the  place  of  the  softer  metals, 
copper,  and  its  alloys,  and  the  effect  upon  the  his- 
tory of  mankind  was  enormous.  Iron,  because  of 
its  superior  hardness  and  stiffness,  would  take  a 
sharper  edge,  would  keep  it  longer,  could  be  made 
into  more  slender  tools  with  finer  points,  or,  in  the 
shape  of  wire  or  thin  bands,  was  stronger  and  more 
rigid  as  a  means  of  binding  things  loosely  together 
or  connecting  them  firmly. 

143 


144          THE    METALLIC    ELEMENTS 

The  chief  effect  of  the  change  to  iron  was  an 
enormous  gain  of  time  in  all  mechanical  work 
where  tools  played  a  part.  For  example,  in  clear- 
ing pieces  of  land  from  trees  or  bushes  by  means  of 
iron  or  steel  instruments,  the  work  could  be  done  in 
a  small  fraction  of  the  time  required  when  men  had 
no  better  tools  than  those  made  of  stone  or  even 
of  copper.  The  nations  or  tribes  that  first  learned 
to  make  weapons  of  iron  and  steel  had  an  enormous 
advantage  over  their  neighbors,  and  often  con- 
quered them.  When  once  discovered,  also,  iron 
proved  to  be  much  more  plentiful  than  copper, 
more  durable  in  use,  and  hence  was,  in  effect, 
cheaper  than  the  softer  metal. 

When  the  history  of  mankind  is  divided  into 
ages,  as  the  Stone  Age,  the  Copper  Age,  the  Bronze 
Age,  the  Iron  Age,  and  the  Steel  Age,  we  shall  have 
covered  in  the  list  its  whole  history  down  to  our 
own  times,  for  we  ourselves  are  living  in  the  last 
of  these.  It  is  to  steel,  merely  a  stiffened  and  more 
elastic  form  of  iron,  that  the  greatest  triumphs  of 
our  times  are  due.  Steel  beams  give  us  our  tower- 
ing city  buildings,  and  our  railroads,  depending 
for  their  efficiency  on  steel  rails  and  steel  locomo- 
tives; our  great  ocean  vessels  have  steel  hulls  and 


THE    METALLIC    ELEMENTS          145 

engines;  our  rivers  are  spanned  by  steel  bridges; 
and  nearly  every  part  of  our  lives  is  dependent 
upon  steel,  either  for  tools  and  weapons,  for  the 
instruments  and  machinery  upon  which  it  depends, 
or  for  the  mechanisms  by  which  these  are  made. 
Every  improvement  in  the  making  of  steel  from  iron 
vastly  increases  the  power  of  mankind.  Even  the 
rarer  metals  most  recently  discovered  largely  take 
their  value  from  the  fact  that  they  can  be  mixed 
into  steel  to  change  its  qualities.  From  the  steel 
pen  that  writes  a  letter,  replacing  the  split  reed  or 
the  shaped  quill,  to  the  great  airship  that  is  prom- 
ised for  the  next  war,  we  are  dependent  upon  iron 
and  its  compounds  for  all  the  'arts  of  war  and 
peace. 

Fortunately,  iron  is  very  plentiful,  but  it  is  sel- 
dom found  in  a  pure  state,  except  in  meteorites. 
The  compounds  of  iron,  however,  are  found 
throughout  nature  in  rocks,  in  many  minerals,  in 
the  soil  itself,  in  most  natural  springs,  and  even  in 
the  coloring  matters  that  make  plants  green  and 
blood  red.  The  most  abundant  compounds  of  iron 
are  hematite,  a  combination  with  oxygen ;  limonite, 
where  iron  is  combined  with  oxygen  and  hydrogen 
in  a  complicated  way ;  magnetite,  another  compound 


146          THE    METALLIC    ELEMENTS 

with  carbon  and  oxygen,  and  siderite,  a  com- 
pound with  carbon  and  oxygen.  Pyrites  is  a  com- 
pound of  iron  with  sulphur.  There  are  other  sul- 
phur compounds  with  iron  also  containing  copper. 

Iron  is  particularly  plentiful  in  the  United 
States,  mainly  in  the  middle  of  the  country  and  in 
the  Lake  Superior  region.  Chemists  and  engineers 
are  constantly  at  work  studying  how  to  improve 
methods  of  extracting  iron  from  its  ores,  and  as  a 
result,  iron  is  constantly  cheapened. 

The  usual  method  of  extracting  iron  from  its 
oxide  ores  is  to  crush  and  grind  the  ores  and  then 
to  subject  them  to  intense  heat,  with  coke  or  coal 
and  limestone,  in  a  blast  furnace.  Under  the  in- 
tense heat  of  a  forced  draft,  the  hot  air  causes  the 
oxygen  and  carbon  to  unite,  leaving  the  melted  iron 
to  collect  at  the  bottom  of  the  furnace.  The  fires 
in  such  a  furnace  may  be  kept  burning  for  months, 
new  ore  being  added  at  the  top  while  the  melted 
iron  is  every  now  and  then  run  into  sand  moulds 
and  allowed  to  cool  in  the  form  of  rough  slabs,  or 
bars,  called  pig-iron. 

Iron  produced  in  this  way  is  not  pure,  but  con- 
tains considerable  carbon,  phosphorus,  and  other 
elements.  Owing  to  its  impurities,  cast  iron  is 


From  Stereograph,  Copyriytit  19C6,  by  Underwood  tf-  Fnderwood,  New  York. 

LOADING   CARS    WITH    IRON   ORE  IN   A   TYPICAL   MINE. 


THE    METALLIC    ELEMENTS          147 

brittle  and  harder  than  pure  iron  would  be.  If 
the  iron  cools  rapidly  the  carbon  in  it  remains 
combined  with  the  iron,  giving  it  a  light  color.  If 


BLAST  FURNACE  DIAGRAM 

Blast  Furnace.  A,  throat;  B,  bosh;  C,  crucible  where  the 
melted  iron  collects;  D,  pipes  for  hot  air  blast;  E,  escape  pipe 
for  gases  which  do  not  escape  through  the  "down  corner  " ;  G, 
cup;  H,  cone;  N,  trough  for  drawing  off  slag;  T,  tuyere;  I, 
hole  through  which  iron  is  withdrawn. 


148         THE    METALLIC    ELEMENTS 

it  cools  slowly,  much  of  the  carbon  remains  in  the 
form  of  graphite,  making  the  iron  grey.  The  lat- 
ter is  the  sort  ordinarily  used  in  foundries,  and  is 
made  into  stoves,  pipes,  fences,  the  heavier  parts 
of  machinery,  and,  in  general,  all  those  things  in 
which  solidity  is  more  important  than  elasticity. 

A  purer  form  of  iron,  containing  less  carbon,  is 
known  as  wrought  iron,  and  has  more  of  the  quali- 
ties of  steel,  being  tougher,  more  malleable,  and 
softer.  This  is  the  form  of  iron  seen  in  iron  wire. 
It  may  be  rolled  into  plates  and  sheets,  made  into 
rods,  chains,  horseshoes,  and,  generally,  into  those 
forms  of  iron-work  where  elasticity  is  desirable. 
It  bends  readily,  does  not  break  as  easily  as  cast 
iron,  and  may  be  readily  formed  into  delicate 
shapes.  It  is  much  used  in  artistic  iron-work. 
Many  things  formerly  made  of  cast  iron  are  now 
constructed  of  steel,  owing  to  the  cheapness  and 
exactness  with  which  steel  may  be  made  of  qualities 
to  suit  the  most  varied  purposes. 

Wrought  iron  is  made  from  ordinary  cast  iron 
by  heating  and  thorough  mixing  so  as  to  burn  out 
much  of  the  impurities.  When  brought  to  the 
right  standard,  the  iron  can  be  rolled  and  ham- 
mered into  shapes  convenient  for  use.  The  process 


THE    METALLIC    ELEMENTS 


149 


corresponds  to  that  used  by  the  smiths  since  early 
times  in  heating  iron  in  their  fires  under  a  blast  of 
air,  and  then  hammering  it  into  shape  upon  an 
anvil.  Wrought  iron  contains  very  little  carbon, 
and  as  it  is  the  carbon  that  gives  stiffness  to  iron, 
it  can  be  readily  understood  that  steel  contains  a 
larger  proportion  of  carbon  than  the  wrought  iron. 


From   Wurte's  "Elements  of  Modern   Chemistry.'* 
APPAEATUS  FOB  ROLLING  STEEL 

To  put  the  matter  shortly,  a  very  large  proportion 
of  carbon  is  found  in  cast  iron ;  a  very  little  carbon 
is  in  wrought  iron;  adding  a  slightly  greater  pro- 
portion of  carbon  to  wrought  iron  converts  it  into 
steel,  which  contains  more  than  one  and  less  than 
the  other.  The  making  of  steel,  however,  is  greatly 
modified  by  the  presence  of  other  elements  beside 
carbon,  and  even  by  the  method  of  its  making. 


150          THE    METALLIC    ELEMENTS 

Steel  may  be  forged,  or  hammered,  into  shape, 
can  be  welded — which  is  to  say,  two  pieces  can  be 
united  simply  by  being  hammered  together  when 
heated.  It  is  harder,  stiffer,  and  more  elastic  than 
iron,  and  finds  many  more  uses.  Its  most  valuable 
and  most  remarkable  quality  is  its  power  of  being 
tempered.  By  heating  the  steel  and  plunging  it 
into  cold  oil  or  water,  it  becomes  exceedingly  brit- 
tle and  hard.  If  heated  and  cooled  very  slowly, 
it  remains  soft  and  malleable.  In  order  to  give  it 
a  quality  between  these  two  extremes,  we  have  only 
to  heat  the  steel,  cool  it  until  it  is  brittle,  and  then 
to  heat  it  once  more.  If  the  second  heating  be 
checked  at  different  points,  we  may  obtain  all  varie- 
ties of  hardness  and  elasticity.  This  reheating  is 
known  as  tempering.  As  the  steel  is  reheated  it 
shows  different  colors  upon  its  surface,  and  these 
changing  colors  tell  just  what  the  result  of  cooling 
the  steel  will  be  at  each  moment.  Experiments 
have  shown  that  the  following  colors  are  produced 
successively  at  the  following  temperatures : 


THE    METALLIC    ELEMENTS          151 

430°  Fahrenheit.  Very  pale  yellow — Lancets. 

450°  "  Light  straw  color — Razors  and  surgeons' 

instruments. 

490°  "  Brownish  yellow — Scissors  and  chisels. 

510°  Purplish  brown — Axes  and  planes. 

530°  "  Purple— Table  knives. 

550°  "  Light  blue — Springs  and  saws. 

560°          "  Dark  blue— Augers. 

600°  "  Blackish       blue— Handsaws,       hardest 

drills. 

By  selecting  the  proper  color,  the  hardness  and 
toughness  of  the  steel  may  be  governed.  For  tools 
meant  to  be  rather  tough  than  hard,  the  heat  is 
checked  while  the  steel  is  yellow  or  brown.  To 
make  exceedingly  hard  tools  for  drilling  or  similar 
uses,  the  heating  is  checked  only  when  the  steel 
shows  blue. 

There  are  many  different  substances  used  for 
cooling  heated  steel.  The  commonest,  of  course, 
is  water,  but  many  different  kinds  of  oils,  metallic 
solutions,  animal  fats,  and  even  mercury,  are  em- 
ployed to  give  different  qualities  to  steel.  The 
effects  of  various  elements  upon  steel  may  be  gener- 
ally stated  as  follows:  Carbon  hardens  and  tough- 
ens the  metal ;  silicon  hardens,  but  lessens  the  duc- 
tility, or  the  quality  of  being  drawn  into  wire; 


152          THE    METALLIC    ELEMENTS 

phosphorus  makes  steel  brittle  under  shock,  sul- 
phur makes  steel  difficult  to  work ;  manganese,  like 
phosphorus,  seems  to  increase  brittleness,  if  pres- 
ent in  too  great  quantities;  copper  seems  to  do  no 
harm  unless  sulphur  is  present  with  it ;  aluminium, 
nickel  and  chromium  toughen  steel ;  arsenic  hardens 
it.  It  is  believed  that  the  best  results  are  ob- 
tained when  the  steel  is  made  entirely  of  iron  and 
carbon,  though  small  quantities  of  other  elements 
often  render  steel  suitable  for  special  uses. 

The  manufacture  of  steel,  after  what  has  been 
said,  will  be  seen  to  consist  in  securing  iron  with 
the  right  amount  of  carbon.  This  can  be  done 
either  by  taking  carbon  from  cast  iron  or  adding 
it  to  wrought  iron,  either  directly  or  by  means  of 
adding  cast  iron  to  the  wrought  iron.  It  is  found 
easiest  to  add  the  carbon  to  wrought  iron.  This  is 
done  either  by  packing  iron  with  carbon  in  tight 
crucibles,  or  by  first  burning  carbon  out  from  cast 
iron  and  then  restoring,  by  adding  to  cast  iron  the 
right  amount  of  carbon.  This  last  is  the  method 
used  in  the  Bessemer  process,  which,  invented  in 
1860,  has  been  most  generally  adopted  and  has  been 
found  to  make  steel  of  any  desired  quality  cheaply 
and  readily.  The  apparatus  in  which  this  is  done  is 


THE    METALLIC    ELEMENTS          153 

known  as  a  converter — a  great  oval  box  large 
enough  to  hold  several  tons  of  melted  iron. 
Through  the  molten  iron  air  is  blown,  and  the  car- 
bon thus  burned  out, — the  oxygen  of  the  air  unit- 
ing with  it  forming  the  inflammable  gas,  carbon 
monoxide.  This  burns  at  once,  keeping  the  metal 


CONVERTER 

melted,  and  after  a  few  minutes  only,  the  carbon 
and  silicon  and  other  impurities  being  thus  re- 
moved, enough  cast  iron  can  be  added  to  give  any 
desired  mixture  of  carbon. 

There  is  another  process  by  which  sulphur  and 
phosphorus  can  be  removed  in  a  similar  way.  A 
third  process  consists  in  burning  out  impurities 
on  an  open  hearth  by  means  of  a  flame  containing 


154 


THE    METALLIC    ELEMENTS 


much  oxygen.  This  is  known  as  the  open-hearth 
process,  and  is  especially  useful  in  making  tough 
and  elastic  steel,  much  used  where  it  is  meant  to 
stand  a  great  strain,  as  in  cannon,  parts  of  large 
machines,  bridge  beams,  rails,  and  building  beams. 
Pure  iron  is  seven  and  eight- tenths  times  as 


MAGNETS — HENRY'S  (A).    STURGEON'S  (B) 

Sturgeon's  was  the  early  form,  Henry's  is  the  modern  im- 
provement, by  putting  many  turns  of  the  wire  on  spools  through 
which  the  poles  are  thrust. 


heavy  as  water.  It  is  a  metal  having  the  remark- 
able quality  of  becoming  instantly  magnetic  when 
surrounded  by  an  electric  current,  and  of  losing 
this  magnetism  as  soon  as  the  current  is  withdrawn. 
Steel,  on  the  contrary,  once  magnetized,  retains  the 
magnetism.  It  is  believed  that  these  two  results 
depend  upon  the  fact  that  in  steel  the  particles, 


THE    METALLIC    ELEMENTS          155 

once  magnetized,  arrange  themselves  in  a  fixed  posi- 
tion, whereas,  in  iron,  the  position  of  the  particles 
is  retained  only  while  the  current  is  passed.  The 
importance  of  this  quality  of  iron  can  hardly  be 
over-estimated.  Most  of  the  mechanical  applica- 
tions of  electricity  depend  upon  it.  To  it  we  are 
indebted  for  the  telephone,  telegraph,  dynamos, 
motors,  electro-magnets,  and  all  other  applications 
of  the  electro-magnet. 

Pure  iron  in  the  presence  of  water  or  moisture 
rusts,  that  is,  forms  a  ferric  hydroxide,  which  is  a 
complicated  compound  of  iron,  oxygen,  and  hydro- 
gen. Bust  formed  on  the  surface  of  iron  does  not 
prevent  further  rusting,  but  the  rust  will  proceed 
until  the  whole  mass  of  iron  is  changed  to  the  ox- 
ide, because  iron-rust  and  iron,  when  moist,  make 
up  an  electric  couple,  and  thus  continue  the  rusting 
or  oxidizing.  This  will  be  better  understood  after 
reading  about  electrolysis,  later  in  this  book.  This 
makes  it  necessary  to  protect  iron  from  the  air  by 
means  of  paints  or  oils,  or  by  forming  chemically 
upon  its  surface  some  compound  of  iron  that  will 
not  further  combine  with  the  oxygen  and  hydrogen. 

The  compounds  of  iron,  like  those  of  copper,  are 
divided  into  two  general  classes  according  to  the 


156          THE    METALLIC    ELEMENTS 

amount  of  iron  contained  in  them.  They  are 
known  as  ferrous  and  ferric  salts.  Owing  to  the 
fact  that  the  ferrous  salts  readily  unite  with  oxy- 
gen, they  tend  to  change  in  the  air  into  the  ferric 
salts,  and  this  same  change  can  be  hastened  by  the 
chemist,  if  he  chooses,  through  the  use  of  acids 
which  bring  about  a  rapid  combination  with  oxy- 
gen. The  ferrous  salts  tend  to  have  a  greenish 
color.  Among  them  may  be  mentioned  green  vit- 
riol, which  is  used  in  the  laboratory  as  a  reducing 
agent,  that  is,  an  agent  for  removing  oxygen  from 
compounds.  It  also  finds  commercial  use  in  the 
making  of  dyes  and  inks.  The  inks  which  are  made 
from  iron  salts  combined  with  tannin  are,  in  gen- 
eral, of  two  classes ;  one  which  writes  black  at  once, 
and  another  which  becomes  black  after  drying,  ow- 
ing to  the  action  of  the  oxygen  in  the  air  upon  the 
iron. 

Ferric  salts  tend  toward  reddish  brown  and  pale 
violet  in  color.  Thus  the  ferric  oxide  is  a  brown- 
ish-red salt  which  is  used  to  make  chalk,  and  red 
ochre  in  painting.  It  is  also  a  polishing  material 
and  gives  color  to  porcelain  and  glass.  These 
colors  vary  according  to  the  treatment.  The  ferric 
hydrate  is  yellow  ochre,  and  may  be  considered  sim- 


.From  Stereograph,   Copyright  1906,  &y  Under woorl  ,f-  Underwent,  New  York. 

OPEN  PIT  IRON  MINING. 


THE    METALLIC    ELEMENTS          157 

ply  as  iron  rust.  Besides  these,  there  are  a  ferric 
sulphate,  ferric  chloride,  and  other  compounds, 
from  the  simplest  to  those  whose  composition  re- 
quires the  deepest  study.  There  are  hundreds  of 
compounds  of  iron,  but  we  may  say,  in  general, 
that  besides  their  uses  in  the  laboratory,  they  are 
mainly  employed  in  medicine  and  in  making  dyes 
and  inks,  and  in  photography.  Their  value  con- 
sists in  their  coloring  property,  in  their  affinity  for 
oxygen,  and  in  the  solubility  of  many  of  them  in 
water. 

COBALT  AND  NICKEL 

Cobalt  is  a  metal  discovered  in  1733.  It  has  a 
white,  metallic  lustre,  somewhat  resembles  iron  in 
hardness,  but  is  more  fusible  and  less  magnetic. 
It  has  an  affinity  with  oxygen,  and  thus  rusts  in 
the  air,  though  to  a  less  extent  than  iron.  The 
metal,  when  pure,  is  rare,  being  usually  found  com- 
bined with  nickel,  with  arsenic,  or  with  antimony. 
It  has  no  especial  use  yet  discovered.  It  forms 
salts  with  nitric,  hydrochloric,  or  sulphuric  acid, 
and  these  are  reddish  in  color,  but  become  blue 
when  heated,  the  heat  driving  off  the  water  con- 
tained in  their  crystals. 


158         THE    METALLIC    ELEMENTS 

Cobalt  combined  with  silica  forms  a  coloring 
matter  known  as  smalt,  a  beautiful  blue  color  used 
in  coloring  pottery  and  glass.  Cobalt  gives  other 
valuable  pigments  for  painters  and  in  the  arts 
generally. 

Nickel  somewhat  resembles  both  iron  and  cobalt, 
but  is  commoner  than  the  latter.  The  quality  that 
makes  it  most  valuable  is  the  fact  that  it  retains 
its  brightness  in  the  air,  that  is,  it  does  not  combine 
with  oxygen.  Nickel  is  also  used  as  an  alloy  with 
copper,  a  very  small  quantity  serving  to  lighten 
the  color  of  that  metal.  Alloyed  with  brass,  nickel 
gives  us  German  silver,  a  valuable  alloy  because 
of  its  resistance  to  oxygen,  or  because  it  does  not 
rust.  Nickel  is  added  to  steel,  to  which  it  gives 
the  greatest  toughness.  A  little  over  three  per 
cent,  of  nickel  has  been  found  to  make  the  best 
alloy  of  steel  for  manufacturing  armor  plates  and 
parts  of  machinery  where  extreme  strength  is  requi- 
site. An  every-day  use  of  nickel  with  which  we  are 
all  familiar  is  in  nickel-plating.  This,  because  of 
the  high  polish  which  nickel  takes,  not  only  ren- 
ders manufactured  articles  attractive,  but  it  is  use- 
ful as  well,  since  it  protects  steel  and  iron  from 
rusting.  Nickel-plating  is  sometimes  applied  to 


THE    METALLIC    ELEMENTS          159 

zinc,  thus  giving  an  alloy  which  is  capable  of  re- 
ceiving a  very  high  polish  and  at  the  same  time  is 
light  and  durable,  while  it  is  easily  moulded  into 
articles  from  sheet  metal. 

Nickel  and  iron  are  likely  to  occur  pure  only  in 
meteorites.  Like  iron,  nickel  may  be  welded  when 
free  from  carbon,  silicon,  and  other  impurities. 
In  general  properties  iron  and  nickel  resemble  one 
another  closely,  differing  only  in  their  affinity  for 
oxygen. 


CHAPTER    XI 

METALLIC  ELEMENTS,  CONTINUED 

PLATINUM 

PLATINUM  is  a  very  heavy  metal,  with  a  strong 
resemblance  in  appearance  to  silver,  though  it  is 
greyer  and  does  not  take  so  high  a  polish.  It  is 
found  in  an  ore  which  contains  also  five  exceed- 
ingly rare  metals  in  small  quantities.  These  are 
ruthenium,  osmium,  iridium,  rhodium,  and  palla- 
dium. Iron,  gold,  and  copper  are  often  found 
associated  with  these.  Most  of  the  platinum  ore 
comes  from  Russia,  though  small  quantities  are 
found  in  the  United  States,  South  America,  and 
other  countries.  The  name  is  derived  from  the 
Spanish,  plata,  which  means  silver,  and  was  given 
because  the  metal  was  supposed  long  ago  to  be  a 
form  of  silver  ore.  The  ore  occurs  in  the  form  of 
grains  or  scales,  and  is  at  first  treated  with  strong 
acids  to  remove  gold,  silver,  and  copper.  This 
changes  platinum  into  a  solution  which  contains 
some  iridium.  By  adding  ammonium  chloride  the 

161 


1G2          THE    METALLIC    ELEMENTS 

platinum  is  precipitated  and  may  then  be  ham- 
mered into  sheets. 

Owing  to  its  strong  resistance  to  nearly  all  acids, 
platinum  is  used  in  the  laboratory  for  making  cru- 
cibles, stills,  dishes,  and  other  vessels  to  contain 
acids  that  would  attack  other  metals.  Platinum 
also  resists  heat,  and  may  therefore  be  used  in 
heating  compounds  when  vessels  made  of  other 
materials  would  be  melted.  A  very  important  use 
of  platinum  depends  upon  the  fact  that  when 
heated,  or  cooled,  it  expands  and  contracts  to  prac- 
tically the  same  degree  as  glass.  Consequently  it 
may  be  used  in  connecting  electric-light  bulbs  to 
electric  wires.  When  the  current  passes  into  the 
bulb  it  heats  the  connecting  wires,  and  these  ex- 
pand. If  these  wires  did  not  expand  and  contract 
at  the  same  rate  as  the  substance  of  the  glass  bulbs, 
they  would  either  cause  the  bulbs  to  crack,  or  would 
admit  air,  thus  destroying  the  vacuum.  But  where 
platinum  is  used,  the  joint  remains  tight.  No  other 
metal  has  been  found  to  take  its  place  for  this 
purpose. 

Platinum  is  used  also  by  dentists,  owing  to  its 
resisting  power  to  corrosion.  For  the  same  reason 
it  is  used  in  jewelry,  making  a  good  contrast  with 


THE    METALLIC    ELEMENTS          163 

gold  and  furnishing  exactly  the  right  setting  for 
certain  jewels.  Owing  to  its  use  in  electric  work, 
the  demand  for  platinum  largely  exceeds  the  sup- 
ply, and  its  price  is  continually  increasing.  Plati- 
num is  exceedingly  heavy,  even  heavier  than  gold, 
being  twenty-one  times  as  heavy  as  water.  There 
are  only  a  few  elements  which  are  heavier,  such 
as  osmium  and  iridium. 

Platinum  conducts  electricity,  but  has  a  very 
high  resistance,  which  causes  it  to  give  out  a  large 
amount  of  light  and  heat.  Platinum  is  largely 
used  in  photography  because  of  its  beautiful  black 
color  when  minutely  divided,  and  its  permanence, 
owing  to  the  fact  that  it  does  not  tarnish  or  oxi- 
dize. The  chief  obstacle  to  its  use  for  the  making 
of  photographic  prints  is  its  rarity  and  very  high 
price. 

A  peculiar  property  of  platinum,  while  in  the 
spongy  state,  or  when  very  finely  divided,  is  the 
ability  to  absorb  very  large  volumes  of  gases.  The 
absorption  of  gas  is  so  rapid  that  heat  is  given 
out  rapidly  enough  to  set  fire  to  the  gas.  This 
same  property  is  found  in  palladium.  It  is  known 
as  occlusion.  Owing  to  this  property,  small  quanti- 
ties of  platinum  are  sometimes  used  to  make  light- 


164          THE    METALLIC    ELEMENTS 

ers  on  gas-burners.  As  soon  as  the  gas  is  turned 
on,  its  absorption  by  the  platinum  begins,  the  plati- 
num is  soon  red-hot,  and  the  gas  takes  fire.  A 
pocket  cigar-lighter  is  made  on  the  same  principle. 
A  small  metal  box  contains  a  wick  saturated  with 
a  liquid  that  gives  off  gas  readily.  Another  com- 
partment of  the  box  holds  a  bit  of  platinum  wire, 
which,  by  being  thrust  into  the  fumes,  becomes 
heated  and  ignites  the  vapor,  as  already  explained. 

Of  the  rarer  metals  often  found  with  platinum, 
palladium  is  sometimes  used  in  the  laboratory  be- 
cause of  its  ability  to  absorb  gases,  especially  hydro- 
gen ;  osmium  is  used  in  a  certain  form  of  electric 
light  and  in  chemical  work  under  the  microscope; 
while  iridium  is  used  in  making  an  alloy  to  tip 
gold  pens,  as  it  is  intensely  hard  and  almost  un- 
wearable.  Some  chemists  make  a  large  group  of 
nine  metals,  which  they  call  the  platinum  group. 
In  this  are  included  iron,  cobalt,  ruthenium,  rho- 
dium, palladium,  osmium,  iridium,  and  platinum. 
They  are  grouped  together  because  all  are  hard, 
white,  not  easily  melted,  and,  excepting  iron,  are 
not  attacked  by  the  air. 

To  finish  the  discussion  of  this  group  by  a  few 
words  about  the  rarer  metals,  ruthenium  is  called 


THE    METALLIC    ELEMENTS          165 

the  rarest  of  the  elements;  rhodium  also  is  very 
rare ;  palladium  has  interest  for  us  mainly  because 
of  its  property  of  absorbing  hydrogen.  This  ab- 
sorption increases  the  size  of  the  mass  of  metal 
and  takes  place,  as  has  been  said,  rapidly  enough 
to  cause  a  high  temperature,  as  in  the  case  of  plati- 
num. Kadium  is  still  being  studied,  and  therefore 
cannot  be  finally  assigned  its  place  in  a  table  or 

system  of  elements. 

ARSENIC 

Arsenic,  when  pure,  is  a  brittle,  grey  solid,  about 
five  or  six  times  heavier  than  water.  When  heated 
it  changes  to  vapor,  with  a  smell  like  that  of  garlic. 
Its  chief  practical  use  is  to  form  poisons  for  ani- 
mals, as  a  drug,  in  minute  quantities  in  medicine, 
and  to  harden  lead,  a  very  small  portion  being 
added  to  the  lead  from  which  shot  is  made.  Ar- 
senic also  occurs  in  many  green  paints,  enters  into 
the  manufacture  of  glass,  and  is  especially  useful 
in  preserving  skins  from  the  attacks  of  insects. 
Paris-green  is  a  common  insect  poison,  containing 
a  large  quantity  of  arsenic.  The  symbol  for  arsenic 
is  As.  In  spite  of  the  fact  that  the  element  arsenic 
itself  is  not  poisonous,  its  compounds  are  among 
the  most  poisonous  of  all  substances.  Fortunately 


166          THE    METALLIC    ELEMENTS 

it  can  be  readily  detected,  even  in  the  most  minute 
quantities.  Arsenic  coloring  matters  are  very  dan- 
gerous. In  wall  papers  or  clothing  or  draperies, 
the  arsenic  may  become  detached  and  be  absorbed 
or  breathed  as  a  gas.  For  this  reason  brilliant 
green  colors  in  food,  dyes,  wall  papers,  and  so  on, 
should  be  avoided  unless  they  are  known  to  be  free 
from  arsenic.  Symptoms  of  arsenic  poisoning  are 
dryness  of  the  mouth,  headache,  and  nausea,  or, 
if  the  poison  takes  the  form  of  a  gas,  muscular 
pains  and  inability  to  sleep. 

ANTIMONY 

The  symbol  for  this  element  is  Sb,  from  the  Latin 
name  stibium.  It  is  a  silver-white  solid,  found 
usually  in  crystals,  a  little  heavier  than  arsenic. 
As  it  expands  instead  of  contracting  when  cooled, 
antimony  is  added  to  type  metal  so  that  the  metal 
on  cooling  may  fill  up  the  tiniest  parts  of  the  mould, 
forming  perfect  type. 

Antimony  is  also  used  in  the  alloys  known  as 
Britannia  metal  and  Babbitt  metal,  and  with  bis- 
muth, it  forms  a  very  effective  thermopile.  The 
thermopile  is  a  means  of  causing  electricity  to  be 
produced  by  heating  or  cooling  two  metals  joined 


THE    METALLIC    ELEMENTS          167 

together,  an  arrangement  often  found  useful  in  cer- 
tain apparatus.  Excepting  these  uses,  antimony  is 
found  commercially  useful  only  in  making  some 
kinds  of  matches  and  fireworks,  and  in  the  prepa- 
ration of  rubber.  It  is  also  one  of  the  constituents 

of  tartar  emetic. 

LEAD 

Lead  has  been  known  since  the  earliest  days, 
being  called  plumbum  by  the  Romans,  which  gives 
us  our  symbol  for  the  element,  Pb.  It  is  occasion- 
ally found  pure  in  nature,  but  the  most  abundant 
ore  is  galena,  which  is  lead  sulphide,  and  it  is  from 
this  ore  that  the  lead  of  commerce  is  derived.  A 
large  quantity  is  produced  in  the  middle  west  of 
the  United  States.  The  ore  is  subjected  to  heat  in 
a  furnace,  and  the  metal  readily  separates  from  the 
sulphur,  which  combines  with  oxygen,  or  sometimes 
with  iron,  which  is  added  for  the  purpose.  Lead 
is  also  separated  from  the  galena  by  the  electric 
current,  using  sulphuric  acid  as  the  electro- 
lyte. 

It  is  a  bluish  metal,  showing  a  bright  surface 
when  cut  or  scraped.  It  soon  tarnishes  in  the  air 
by  forming  an  oxide,  but  once  formed,  this  coating 
protects  the  metal  within.  It  is  the  heaviest,  ex- 


168          THE    METALLIC    ELEMENTS 

cept  mercury,  of  the  common  metals,  and  melts 
readily  at  a  low  heat. 

The  salts  of  lead  are  poisonous,  and  if  taken  into 
the  body  gradually  accumulate  there,  with  serious 
effects.  Commercially,  lead  finds  its  greatest  use 
in  piping,  made  by  forcing  lead  through  a  hole 
in  which  is  a  core.  This  piping  is  used  both  for 
conveying  water  and  to  cover  the  wires  that  con- 
duct electricity.  It  is  also  used,  of  course,  in  the 
making  of  shot  and  bullets,  though  these  are  nowa- 
days often  alloys. 

To  make  type  metal,  lead  is  alloyed  with  anti- 
mony, because  the  latter  metal  has  the  property  of 
expanding  while  cooling,  as  already  mentioned. 
Massicot  and  litharge  are  the  monoxides  of  lead 
(PbO),  and  are  used  in  oils  and  varnishes  and  in 
making  glass.  Ked  lead  (Pb3O4)  is  used  in  making 
glass  and  as  an  artists'  paint.  The  cheaper  form 
of  red  lead  is  often  used  as  a  priming,  in  painting, 
to  protect  iron  structures  from  rust,  and  also  to 
make  tight  the  joints  of  lead  pipes.  The  old  name 
was  minium,  and  the  use  of  this  red  color  by  il- 
luminators for  initials  in  books  written  by  hand 
gives  us  the  word  "  miniature,"  applied  at  first  to 
small  ornamental  pictures  that  went  with  the  red 
initial  letters. 


THE    METALLIC    ELEMENTS          169 

White  lead  is  a  lead  carbonate  (PbCO3).  It  is  a 
heavy  white  powder,  used  as  a  white  paint  when 
mixed  with  linseed  oil.  It  is  prepared  by  many 
processes,  the  older  processes  being  very  slow,  but 
the  electric  process  is  rapid  and  said  to  be  as 
good. 

Sugar  of  lead  is  the  lead  acid  formed  by  the  ac- 
tion of  acetic  acid  upon  lead,  or  lead  oxide.  It  is 
exceedingly  poisonous.  There  are  many  other  com- 
pounds of  lead,  but  they  are  less  important. 

TIN 

Tin  is  one  of  the  oldest  of  the  metals,  the  mines 
in  the  British  Islands  having  been  known  long  be- 
fore the  Christian  Era,  being  visited  by  the  Phoeni- 
cians. The  islands,  indeed,  were  known  as  the 
Cassiterides,  or  Tin  Islands,  from  the  Greek  word 
Kao-o-tVe/oos.  The  Latin  name  for  the  metal  is  stan- 
num,  which  gives  us  the  symbol  Sn.  While  softer 
than  zinc,  it  is  harder  than  lead,  and  a  little  over 
seven  times  as  heavy  as  water.  As  it  is  not  easily 
affected  by  air  or  moisture  or  weak  acids,  a  coating 
of  it  is  used  to  protect  sheet  iron,  which  forms 
"  tinware."  The  so-called  tin  foil  should  be  made 
of  hammered  tin,  but  is  usually  formed  partly  of 


170          THE    METALLIC    ELEMENTS 

lead.  Tin  is  used  largely  to  make  alloys  with 
copper,  and  lead  with  tin  forms  pewter  and 
solder. 

When  a  bar  of  pure  tin  is  bent,  it  produces,  owing 
to  the  crystals  present,  a  peculiar  noise,  known  as 
the  "  cry  "  of  tin. 

MERCURY,   ZINC,    MAGNESIUM,   AND  CADMIUM 

Mercury  is  the  metal  that  exists  in  liquid 
form  at  ordinary  temperatures.  Its  symbol  is  Hg, 
and  its  common  name  is,  of  course,  quicksilver. 
The  symbol  comes  from  the  Latin  name,  hydrar- 
gyrum, which  means  water  silver.  Mercury  has 
been  known  since  the  earliest  days,  and  occurs 
mainly  in  the  important  ore,  cinnabar,  especially 
abundant  in  Spain.  The  mercury  is  extracted  from 
this  ore,  which  is  a  sulphide,  by  heating,  whereupon 
the  sulphur  combines  with  oxygen,  and  the  mercury 
is  changed  to  vapor,  and  may  then  be  condensed. 
Pure  mercury  is  a  bluish  white  liquid,  which  boils 
at  674  degrees  Fahrenheit.  It  does  not  freeze  until 
the  temperature  reaches  about  35  below  zero.  It 
is  nearly  fourteen  times  as  heavy  as  water.  It  is 
one  of  the  elements  each  molecule  of  which  consists 
of  a  single  atom.  It  is  used  in  the  extraction  of 


THE    METALLIC    ELEMENTS          171 

gold  and  silver  from  their  ores,  to  make  barometers 
and  thermometers,  and  especially  in  the  so-called 
mercury  pump,  used  to  extract  the  air  from  incan- 
descent bulbs.  When  made  into  an  alloy,  it  is 
called  an  amalgam.  Amalgams  are  used  in  tinning, 
gilding,  and  silvering,  to  cover  the  zinc  plates  in 
electric  batteries,  and  to  protect  metals  from  rust- 
ing. In  medicine,  mercury  is  a  most  important 
drug,  especially  used  in  blood-poisoning  and  in 
liver  troubles,  being  the  chief  constituent  of  calo- 
mel. Mercury  is,  however,  a  poison  to  the  system, 
producing  palsy,  salivation,  and  other  symptoms. 
Another  use  is  the  silvering  of  mirrors,  for  which 
purpose  mercury  is  made  into  an  amalgam  with 
tin.  Amalgams  made  with  silver  or  platinum  are 
used  by  dentists  for  filling  teeth.  Mercury  chloride, 
the  common  name  for  which  is  corrosive  sublimate, 
is  a  white  solid,  with  acid  properties,  exceedingly 
poisonous,  but  used  in  minute  quantities  in  medi- 
cine, being  one  of  the  very  best  antiseptics.  Mer- 
cury iodide  is  used  as  a  paint. 

The  sulphide,  cinnabar,  occurs  in  two  forms,  red 
and  black,  the  latter  being  artificial.  The  red, 
when  pure,  gives  the  brilliant  "  vermilion,"  whose 
uses  are  manifold.  Fulminating  mercury  is  a  com- 


172         THE    METALLIC    ELEMENTS 

plicated  compound,  with  the  formula,  HgN2C2O2. 
It  is  a  white  powder,  used  to  make  percussion  caps, 
and  so  easily  exploded  that  the  very  slightest  dis- 
turbance, such,  for  example,  as  removing  the  cork 
from  a  bottle,  is  sometimes  sufficient  to  set  it  off. 

ZINC 

With  mercury  are  often  grouped  zinc,  magne- 
sium, and  cadmium.  Zinc  ores  are  combined  with 
sulphur,  carbon,  silicon,  and  oxygen.  The  sulphur 
compound  is  found  in  Missouri  and  Kansas.  The 
zinc  is  separated  from  its  ores  by  heating  with 
charcoal,  and  the  liquid  zinc  is  then  vaporized  and 
cooled  again  to  separate  impurities.  It  is  a  shiny 
white  metal  that  is  brittle  until  it  has  been  worked 
over.  Though  it  does  not  tarnish  readily,  grad- 
ually it  darkens  in  the  air. 

It  finds  an  extensive  use  in  electric  batteries, 
for  which  purpose  it  is  coupled  with  copper  or 
with  carbon  to  make  the  two  poles.  Sheet  zinc  is 
used  to  line  tanks,  or  to  protect  walls  or  floors  from 
heat.  The  coating  of  zinc  on  iron  is  used  to  pro- 
tect it  from  rust,  and  such  iron  is  commonly  known 
as  galvanized.  Zinc  enters  into  many  alloys,  and 
also  forms  the.basis  for  a  white  paint.  It  is  very 


THE    METALLIC    ELEMENTS          173 

permanent  because  it  does  not  change  when  exposed 
to  the  air.  Zinc  sulphate  is  used  in  medicine,  and 
also  in  dyeing  and  cloth-printing.  A  wide  use  of 
zinc  in  sheets  is  in  roofs,  gutters,  ornamental  cor- 
nices, and  so  on.  A  chloride  of  zinc  is  injected  into 
wood  to  prevent  decay.  An  oxide  of  zinc,  already 
spoken  of  as  being  used  as  a  pigment,  is  also  some- 
times used  for  tooth  filling.  The  symbol  of  zinc 
is  Zn,  and  it  melts  at  a  little  above  the  temperature 
at  which  coal  lights,  being  less  fusible  than  lead 
or  tin,  but  far  more  fusible  than  iron. 

CADMIUM 

Cadmium,  the  symbol  of  which  is  Cd,  is  often 
found  in  zinc  ores,  from  which  it  is  separated  before 
the  zinc,  being  more  easily  made  volatile.  It  re- 
sembles tin  in  color,  and  is  more  malleable  and 
ductile  than  zinc.  It  melts  at  a  slightly  higher 
temperature  than  lead.  The  chief  use  of  cadmium 
is  in  cadmium  sulphide,  a  bright  yellow  solid  used 
as  a  pigment  and  making  a  brilliant  and  permanent 
yellow.  Cadmium  also  forms  certain  alloys  that 
melt  readily. 

MAGNESIUM 

Magnesium  (Mg)  is  found  very  widely  distrib- 


174          THE    METALLIC    ELEMENTS 

uted  in  its  compounds,  and  is  so  abundant  as  to 
form  over  two  per  cent,  of  the  earth's  crust.  In  the 
upper  Mississippi  Valley  a  magnesium  calcium  car- 
bonate, called  dolomite,  and  resembling  marble  and 
limestone,  forms  vast  deposits,  and  even  mountain 
ranges.  Magnesium  is  found  in  many  silicate 
rocks,  and  also  in  sea  water  and  mineral  springs. 
It  is  named  from  its  occurrence  in  Magnesia,  a 
district  of  Thessaly.  Its  melting  point  is  high, 
about  806°  Fahrenheit.  Magnesium  occurs  in  talc 
and  in  soapstone,  a  more  compact  form  of  the  same 
mineral,  also  in  asbestos.  Magnesium  sulphate, 
known  as  Epsom  salts,  is  found  in  many  springs 
in  the  neighborhood  of  Epsom,  England.  Some 
compounds  are  used  as  fertilizers,  and  in  making 
medicines. 

Two  striking  properties  of  magnesium  are  its 
lightness,  and  the  fact  that  it  burns  readily,  giving 
a  most  brilliant  light,  often  used  in  flashlights  for 
photography,  and  also  formerly  in  magic  lanterns. 
Phosphates  of  magnesium  occur  in  the  bones  of 
animals,  in  grains,  and  seeds,  and  in  guano,  which 
renders  the  latter  valuable  as  a  fertilizer.  Magne- 
sium oxide,  often  called  magnesia,  is  used  in  medi- 
cine as  an  antidote  for  poisoning  with  mineral 


THE    METALLIC    ELEMENTS          175 

acids,  and  since  it  hardens  on  exposure  to  the  air 
when  mixed  with  water,  is  a  useful  compound  in 
forming  artificial  stones,  or  gems. 

ALUMINIUM   OR  ALUMINUM 

Next  to  oxygen  and  silicon,  compounds  of  alu- 
minium are  most  plentiful  in  the  earth's  crust. 
Feldspars,  mica,  clay,  and  slate  are  the  commonest 
minerals  in  which  aluminium  is  found.  It  forms 
about  eight  per  cent,  of  the  earth's  crust,  and  is 
therefore  the  most  abundant  of  the  metals.  The 
metal  was  first  obtained,  in  1827,  by  Wohler.  It 
was  prepared  also  in  1854  by  Ste.-Claire  Deville. 
Sir  Humphry  Davy,  on  account  of  the  relation  of 
this  metal  to  alum,  proposed  that  it  be  named  alu- 
mium.  Later  it  was  called  aluminum,  and  finally 
aluminium.  Although  such  vast  quantities  were 
known  to  exist,  the  difficulty  of  extracting  it  was 
so  great  that  the  metal  at  first  obtained  was  hope- 
lessly expensive.  In  1885,  at  the  International 
Exposition,  a  small  bar  of  aluminium  was  exhibited 
in  a  glass  case,  labelled  "  The  silver  from  clay." 
The  showing  of  so  large  a  mass  of  aluminium  was 
the  result  of  a  century's  hard  work  by  chemists. 
The  metal  occurred  in  alumina,  where  it  was  com- 


176          THE    METALLIC    ELEMENTS 

bined  with  oxygen.  In  1824,  (Ersted^  discovered  a 
way  to  make  a  compound  of  chlorine  and  alumin- 
ium, and  from  his  compound,  Wohler,  three  years 
later,  by  the  use  of  metallic  potassium,  separated 
the  aluminium,  since  the  potassium  combined  with 
the  chlorine.  The  metal  as  separated  was  a  fine 
powder,  which  could  not  be  brought  to  unite,  and 
this  powder  remained  a  chemical  curiosity  for 
twenty-seven  years. 

In  1854,  Deville,  by  a  slight  change  in  Wohler's 
process,  obtained  a  button  of  aluminium,  instead 
of  the  powder.  But  this  button  cost  more 
than  its  weight  in  gold.  This  same  chemist  then 
attempted  to  decompose  the  chloride  of  alu- 
minium by  means  of  the  electric  current,  and  thus 
obtained  enough  to  make  a  small  rod.  But  in  those 
days  the  cost  of  electricity  was  too  great  to  make 
the  experiment  a  valuable  one. 

Deville  next  used  sodium,  instead  of  potassium, 
and  this  time  obtained  a  large  quantity  of  alu- 
minium at  less  expense,  part  of  which  was  cast  into 
the  bar  displayed  at  the  Exposition,  and  another 
part  was  made  into  a  rattle  and  presented  to  the 
Prince  Imperial.  A  little  more  of  the  same  metal 
was  cast  into  eagles  for  the  flagpoles  of  the  French 


THE    METALLIC    ELEMENTS          177 

army,  and  made  into  a  helmet  for 'the  King  of 
Denmark. 

No  longer  ago  than  1855,  was  aluminium  thus 
an  almost  priceless  gift  offered  to  the  son  of  an 
emperor.  To-day,  it  is  cheap  enough  to  meet  wide 
use  in  kitchen  utensils  made  of  precisely  the  same 
metal.  By  1860  aluminium  was  being  sold  for  six- 
teen dollars  a  pound,  but  no  improvement  of  impor- 
tance was  made  for  a  quarter  of  a  century.  Other 
investigators  tried  to  improve  the  process,  but  it 
was  not  until  recently  that  the  improvement  in 
electric  machines  and  the  cheapening  of  the  cur- 
rent so  greatly  cheapened  the  metal. 

Without  following  further  the  many  improve- 
ments that  cheapened  its  production,  we  come  to 
what  is  known  as  the  Hall  process,  in  which  elec- 
trolysis made  easy  and  cheap  the  production  of 
hundreds  of  pounds  a  day.  The  cost  of  aluminium 
was  quickly  reduced  to  less  than  fifty  cents  a  pound, 
and  even  this  was  not  the  limit  to  the  cheapening. 

Aluminium  is  only  two  and  a  half  times  as  heavy 
as  water,  or  about  one-third  the  weight  of  iron. 
Its  lightness  is  enormously  important,  and  millions 
of  pounds  of  the  metal  are  produced  a  year  (nearly 
all  at  the  electric  works  at  Niagara  Falls).  It  is 


ITS         THE    METALLIC    ELEMENTS 

easily  drawn  into  wire  or  hammered  into  plates, 
though  it  needs  to  be  annealed  frequently.  It  is 
an  excellent  conductor  of  electricity  and  heat,  and 
its  tensile  strength  is  about  equal  to  that  of  cast 
iron.  Though  readily  cast  and  welded,  it  can  be 
soldered  only  after  taking  great  precautions  to 
bring  together  only  clean  surfaces  of  aluminium. 
It  is  very  slightly  affected  by  the  air,  and  is  little 
affected  by  many  acids.  Clay  would  be  a  cheap  and 
an  inexhaustible  source  of  the  metal,  except  for  the 
presence  of  impurities,  such  as  iron,  silicon,  and 
various  metals  which  make  the  aluminium  brittle. 
It  is  hardly  necessary  to  tell  the  manifold  uses 
to  which  the  metal  has  been  put,  either  for  orna- 
mental purposes,  in  making  protective  paint,  or  for 
light  metal  fixings  of  every  kind.  It  forms  several 
useful  alloys.  Corundum  and  emery  are  oxides  of 
aluminium.  Many  of  the  precious  gems  are  mainly 
aluminium  with  coloring  matter.  The  sapphire,  the 
ruby,  topaz,  amethyst,  and  emerald  (the  latter 
three  in  the  precious  "  Oriental "  variety)  are  all 
crystallized  aluminium  oxide.  Turquoise  is  alu- 
minium phosphate;  the  emerald  is  an  aluminium 
silicate;  the  garnet  also  contains  silicate  of  alu- 
minium. 


THE    METALLIC    ELEMENTS          179 

Alum  is  a  compound  containing  aluminium  sul- 
phate and  potassium  sulphate.  It  is  the  general 
type  of  other  compounds  resembling  it,  also  known 
as  alums.  These  are  very  soluble  in  water,  and 
find  a  wide  use  in  dyeing,  calico  printing,  in  tan- 
ning, in  making  paper,  and  in  fire-proofing  wood 
and  cloth. 

An  important  use  of  alums  is  the  fixing  of  dyes 
in  cloth,  they  being  then  known  as  mordants.  The 
mordant  is  used  to  wet  the  cloth  before  it  is  printed 
with  the  dye,  and  unites  with  the  dye  in  such  a 
manner  as  to  form  a  coloring  compound  that  is  per- 
manent, or  a  fast  color. 

The  clay  which  will  make  pottery  is  aluminium 
silicate,  and  ordinarily  contains  many  impurities. 
According  to  quality,  the  pottery  is  divided  into 
three  classes,  porcelain,  stoneware,  and  earthen- 
ware. 

Aluminium  fuses  at  1292  degrees  Fahrenheit. 
An  important  alloy  is  aluminium  bronze,  which  is 
hard,  malleable,  and  tough  as  steel. 

Aluminium  filings,  with  mercury  chloride  and 
potassium  cyanide,  are  put  together  in  such  a  way 
as  to  produce  great  heat  by  their  combination. 
Then  water  is  added  at  such  a  rate  as  to  reduce  the 


180          THE    METALLIC    ELEMENTS 

temperature  to  about  seventy  degrees.  The  heat 
taken  up  by  the  water  causes  it  to  separate,  the 
oxygen  uniting  with  the  compounds  and  pure  hydro- 
gen being  set  free.  This  method  of  procuring 
hydrogen  is  in  use  in  Paris  for  the  purpose  of  pre- 
paring hydrogen  for  balloons. 

A  modern  application  of  the  readiness  with  which 
oxygen  combines  with  aluminium  is  known  by  the 
name,  Alumino-therniics.  A  mixture  of  aluminium 
and  some  oxide  such  as  iron  rust,  when  lighted  by 
the  magnesium  ribbon  burns  throughout  its  entire 
mass  with  a  fierce  heat  equal  to  that  of  the  electric 
arc.  This  intense  heat  is  used  in  manufacturing 
tools  of  chrome  steel,  in  welding  trolley  rails,  espe- 
cially the  third  rails  that  convey  electricity,  and 
also  may  be  used  on  shipboard  to  weld  large  cast- 
ings such  as  stern-posts  and  propeller-shafts,  when 
broken.  The  thermit  can  be  applied  to  the  break 
without  removing  the  broken  piece  from  its  place, 
and  produces  as  strong  a  welding  as  would  be  pos- 
sible in  a  steel  foundry. 

MANGANESE 

Manganese,  although  not  found  pure  in  nature, 
exists  widely  in  its  compounds,  from  which,  in  its 


THE   METALLIC    ELEMENTS          181 

oxides  especially,  it  is  readily  reduced  by  roasting 
with  charcoal.  It  has  a  high  melting  point,  about 
3500  degrees  Fahrenheit,  and  is  about  seven  and 
a  half  times  as  heavy  as  water.  When  separated, 
the  pure  metal  is  grey,  hard,  and  brittle,  with  a 
lustrous  surface.  Both  physically  and  chemically 
it  resembles  iron  in  many  respects,  entering  into 
similar  combinations.  It  is  especially  useful  in 
forming  alloys,  an  instance  of  which  is  "  spiegelei- 
sen,"  a  valuable  form  of  iron  alloyed  with  man- 
ganese. 

It  forms  many  oxides  which  are  found  in  nature. 
These  find  employment  in  dyeing  and  in  medicine. 
Manganese  also  in  some  compounds  acts  like  an 
acid,  and  gives  rise  to  manganates  and  perman- 
ganates, of  which  those  of  potassium  are  especially 
important,  being  used  in  the  laboratory  as  powerful 
absorbents  of  oxygen,  especially  the  permanganate, 
which  acts  with  great  energy.  This  latter  forms 
the  basis  of  a  disinfectant  known  by  the  name, 
Condy's  fluid. 

Copper  and  iron  with  manganese  form  man- 
ganese bronze,  an  exceedingly  strong  and  tough 
alloy,  possessing  many  of  the  best  qualities  of  steel, 
valuable  because  it  does  not  oxidize,  or  rust.  A 


182         THE    METALLIC    ELEMENTS 

notable  use  of  this  metal  is  the  making  of  pro- 
pellers. A  compound  which  is  most  important  and 
abundant  is  manganese  dioxide,  MnO2.  This,  when 
heated,  sets  free  oxygen,  and  by  the  use  of  hydro- 
chloric acid  may  be  made  to  set  free  chlorine.  This 
dioxide  is  much  used  to  whiten  ordinary  glass,  in 
which  it  neutralizes  the  green  tint. 


CHROMIUM 

Chromium  also  is  found  in  compounds,  never 
free,  but  traces  of  it  occur  in  many  minerals.  Un- 
til the  intense  heat  of  the  electric  furnace  was 
used,  it  was  extracted  with  great  difficulty.  It  is 
a  lustrous  grey  metal,  with  a  shiny  surface  when 
polished.  It  is  slightly  lighter  than  manganese  and 
melts  only  in  the  electric  furnace.  If  a  large  pro- 
portion of  chromium  be  added  to  steel,  it  makes  a 
hardened  steel,  useful  where  the  greatest  resisting 
power  is  needed,  as  in  battleships,  safes,  and  min- 
eral-crushing machines.  With  potassium,  chro- 
mium forms  compounds,  soluble  in  water,  that 
are  valuable  as  oxidizing  agents.  Chrome-alum,  a 
compound  with  sulphur  and  potassium,  is  like  ordi- 
nary alum  except  that  chromium  replaces  the  alu- 


THE    METALLIC    ELEMENTS          183 

minium.  It  is  used  in  dyeing  and  tanning.  Lead 
chromate  is  the  chrome  yellow  which  is  the  basis 
of  the  pigments  called  chromes.  These  are  yellow, 
orange,  or  red. 

There  are  three  rare  metallic  elements  that  may 
be  classified  with  chromium.  These  are  molyb- 
denum, tungsten,  and  uranium.  The  first  enters 
into  certain  laboratory  compounds.  Tungsten  is 
sometimes  used  as  a  hardener  of  steel,  and  fur- 
nishes in  sodium  tungstate  a  fire-proofing  mixture 
for  cloth.  It  has  recently  proved  to  be  exceedingly 
valuable  for  making  filaments  in  incandescent  elec- 
tric lights.  It  needs  a  peculiar  kind  of  support,  and 
at  present  the  filament  is  rather  brittle,  but  if  care 
be  used  it  proves  to  be  a  most  economical  and  effi- 
cient filament,  giving  better  light  at  a  much  de- 
creased cost,  when  compared  with  the  ordinary  car- 
bon filament.  Over  a  million  tungsten  lamps  are 
in  use,  and  about  seventy-five  thousand  a  day  are 
being  made.  It  is  also  used  in  making  incandes- 
cent mantles. 

URANIUM 

Uranium,  the  heaviest  of  all  the  elements,  is  of 
great  scientific  interest,  but  practically  is  used 


184          THE    METALLIC    ELEMENTS 

chiefly  to  color  glass,  to  which  it  gives  the  color 
green  by  transmitted,  yellow  by  reflected,  light, 

BISMUTH 

Bismuth,  though  a  rare  metal,  is  found  free  in 
nature  and  needs  only  to  be  purified.  Its  color  is 
greyish  white,  with  a  reddish  tinge,  and  it  is  brittle. 
It  is  nearly  ten  times  heavier  than  water,  and  melts 
at  a  slightly  higher  temperature  than  does  tin. 
Mixed  with  lead  and  tin,  it  forms  alloys  that  melt 
at  very  low  temperature,  and  find  a  use  as  safety 
plugs,  which  at  a  comparatively  low  temperature 
will  melt.  They  are  used  in  steam  boilers,  to  pre- 
vent short  circuits  in  electric  apparatus,  and  in 
devices  against  fire,  as  in  the  automatic  sprinklers 
of  large  buildings.  Bismuth  and  antimony  form 
an  excellent  combination  for  thermopiles,  that  is, 
when  heated,  an  electric  current  is  set  up  between 
the  metals.  Bismuth  finds  a  small  use  in  medicine. 

STRONTIUM  AND   BAEIUM 

Strontium  and  barium  are  rare,  and  resemble 
calcium  in  many  respects.  The  pure  metals  do  not 
occur  free,  and  find  no  striking  uses.  Their  com- 
pounds are  abundant.  Thus  strontium  hydroxide 


THE    METALLIC    ELEMENTS          185 

is  used  in  the  manufacture  of  beet  sugar.  Stron- 
tium nitrate  enters  into  the  making  of  red  fire. 
Barium  salts  have  a  similar  use  in  making  green 
fire.  Both  of  these  metallic  elements,  combined 
with  sulphur,  are  used  in  making  luminous  paints. 

GLUCINUM 

Glucinum  is  a  silver- white  metal,  light  in  weight, 
resembling  magnesium.  It  never  occurs  free,  but 
is  usually  found  combined  with  silica,  or  alumin- 
ium, or  both.  It  is  found  in  emeralds,  and  in  the 
beryl,  of  which  emerald  is  a  species.  Its  salts  have 
a  sweet  taste  which  gives  it  its  name,  from  the 
Greek  word  glukus,  sweet.  Glucinum  is  also 
called  beryllium. 

NITROGEN,  PHOSPHORUS,  ETC. 

We  have  already,  in  speaking  of  the  composition 
of  the  air,  discussed  to  some  extent  the  properties 
of  nitrogen,  especially  looking  upon  it  as  an  inert 
gas  that  serves  to  dilute  oxygen  and  prevent  its  too 
energetic  action.  But  nitrogen  also  plays  a  most 
active  part  in  its  compounds,  and  especially  in 
nitric  acid  and  ammonia.  It  is  obtained,  as  has 
been  said,  by  removing  oxygen  from  the  air,  and  by 


186 


THE    METALLIC    ELEMENTS 


taking  advantage  of  the  attraction  of  phosphorus 
for  oxygen,  or  by  allowing  liquid  air  to  evaporate — 
a  process  which  to  some  extent  separates  the  two 
gases  composing  it. 

AMMONIA 

Speaking  now  of  its  compounds,  we  shall  take 


PBEPARATION  OF  AMMONIA 

M,  N,  O,  cylinders  containing  solutions  of  impure  ammonium 
chloride,  as  obtained  from  coal  gas  factories,  mixed  with  lime; 
S,  S,  S,  stirrers  to  keep  the  lime  from  settling;  F,  furnace  to 
heat  the  mixture  and  expel  the  ammonia;  B,  B,  condensers  for 
cooling  the  ammonia  gas;  C,  cylinder  of  pure  water  to  absorb 
the  ammonia  and  thus  form  aqua  ammonia;  D,  trough  of  acid 
to  combine  with- any  fluid  escaping  from  C.  In  this  trough  if 
hydrochloric  acid  is  used,  there  would  form  ammonium  chloride. 

up  first  ammonia,  which  common  term  is  applied 
both  to  a  gas  and  to  the  solution  made  when  the 


THE    METALLIC   ELEMENTS          187 

gas  is  dissolved  in  water.  Ammonia  is  formed  nat- 
urally by  the  decaying  of  animal  or  vegetable  mat- 
ters that  contain  nitrogen.  Moisture  supplies 
hydrogen  that  unites  with  this  nitrogen,  forming 
the  gas  ammonia.  One  method  of  preparing  am- 
monia, formerly  much  used,  was  the  heating  of 
horny  substances,  such  as  hoofs  and  horns,  in  a 
closed  vessel,  and  this  gave  rise  to  the  name  still 
popularly  used  for  ammonia — spirits  of  hartshorn. 
The  formula  for  ammonia  gas  is  NH3.  Since  the 
ammonia  gas  is  lighter  than  air,  it  is  collected  in 
the  same  manner  as  hydrogen — by  allowing  it  to 
flow  upward  into  a  vessel  from  which  it  displaces 
air.  Ordinarily,  ammonia  is  prepared  by  mixing 
this  gas  with  water,  which  readily  absorbs  it.  The 
ammonia  in  the  market  is  usually  that  produced 
by  the  distilling  of  coal  in  making  illuminating 
gas.  The  solution  is  correctly  known  chemically 
as  ammonia  hydroxide. 

Ammonia  is  colorless,  with  a  sharp,  choking  odor 
that  makes  it  dangerous  to  inhale.  It  is  only  half 
as  heavy  as  air,  and  readily  separates  itself  from 
solution  if  left  exposed.  Ammonia  can  easily  be 
condensed  to  a  liquid  form  if  reduced  to  a  low 
temperature  under  compression.  When  liquefied, 


188         THE    METALLIC    ELEMENTS 

it  readily  evaporates,  absorbing  much  heat  as  it 
changes  to  the  gaseous  state,  and  is  therefore  widely 
used  in  refrigeration,  as  in  making  artificial  ice. 
The  solution  is  a  very  strong  alkali,  so  strong  as  to 
be  called  one  of  the  caustic  alkalis.  It  neutralizes 
acids,  causing  the  formation  of  salts.  These  salts 
have  a  peculiar  chemical  formula.  In  them  is 
found  a  group  of  atoms  expressed  by  NH4.  This 
group  acts  chemically  as  if  it  were  a  metal,  and  has 
been  given  an  especial  name,  ammonium.  It  can 
be  separated  from  compounds,  since  it  at  once  sepa- 
rates into  ammonia  gas  and  hydrogen.  This  group 
of  one  atom  of  nitrogen  and  four  of  hydrogen,  is 
one  of  those  known  as  a  radical,  because  it  is,  as  it 
were,  a  root  for  the  formation  of  ammonia  com- 
pounds, seeming  to  attach  other  atoms  to  itself, 
and  yet  to  retain  its  formation  as  a  group.  This 
group  is  found  in  several  salts.  With  chlorine  it 
makes  ammonium  chloride;  with  sulphur,  ammo- 
nium sulphate.  The  hydrochloride  is  used  in  elec- 
tric batteries  and  in  several  industries.  It  is  com- 
monly called  muriate  of  ammonia,  because  muri- 
atic, or  hydrochloric  acid,  is  used  in  its  prepara- 
tion. It  is  a  crystalline  solid  that  dissolves  readily 
in  water.  When  heated  gently,  it  turns  to  vapor, 


THE    METALLIC    ELEMENTS          189 

which  is  condensed  upon  the  cooler  surface  of  the 
upper  part  of  the  apparatus  and  can  then  be  col- 
lected. This  method  of  treating  a  solution  so  as  to 
obtain  a  solid  from,  it  is  called  subliming,  or  subli- 
mation. The  result  of  so  treating  ammonium  chlo- 
ride is  to  produce  sal  ammoniac. 

Ammonium  sulphate  is  used  in  fertilizers;  am- 
monium hydrate  is  used  in  the  preparation  of  ni- 
trous oxide,  or  laughing  gas,  so  called  because, 
when  it  is  used  in  producing  insensibility,  during 
the  first  stages  of  its  inhalation  it  causes  a  cer- 
tain pleasurable  excitement  often  expressed  by 
laughter. 

Ammonia  is  used  as  a  slight  stimulant  when  in- 
haled, is  very  valuable  as  a  cleansing  agent,  in 
refrigerating  mixtures,  and  as  a  dye-stuff. 

NITRIC  ACID 

Nitric  acid  is  prepared  by  heating  sulphuric  acid 
with  some  salt  containing  nitrogen;  for  example, 
sodium  or  potassium  nitrate.  The  chemical  for- 
mula expressing  this  formation  is  as  follows: 
NaNO3  +  H2SO4  =  HNO3  +  HNaSO4,  the  HNO3 
being  the  nitric  acid. 

Nitric  acid  is  very  strongly  corrosive,  causing 


190          THE    METALLIC    ELEMENTS 

serious  burns  to  the  skin.  As  it  parts  readily  with 
its  oxygen,  especially  when  warm,  and  this  oxygen 
combines  with  most  other  substances,  these  are 
truly  burned  by  the  acid.  Thus  wood  or  charcoal 
may  be  charred  by  nitric  acid  as  if  in  a  fire.  It 
attacks  the  softer  metals  readily,  and  is  therefore 


APPARATUS  FOB  THE  MANUFACTURE  OF  NITRIC  ACID 
Nitric  acid  is  manufactured  on  a  large  scale  by  heating  sodium 
nitrate  and  sulphuric  acid  in  a  large  cast-iron  retort  A,  con- 
nected with  huge  glass  or  earthen-ware  bottles  B,  B,  B,  ar- 
ranged as  shown.  The  last  bottle  is  connected  with  a  tower 
filled  with  coke  over  which  water  trickles  to  absorb  the  vapors 
which  escape  from  the  bottles.  The  acid  vapors  are  also  often 
absorbed  in  earthenware  or  glass  tubes. 

used  in  etching.  The  etcher  covers  a  plate  of  cop- 
per or  zinc  with  wax,  removes  portions  of  the  wax 
where  he  wishes  lines  to  be  bitten  into  the  metal, 
and  then  covers  the  plate  with  nitric  acid,  usually 
diluted.  The  wax  protects  parts  of  the  metal,  the 
uncovered  lines  being  bitten  in  by  the  eating  away 


THE    METALLIC    ELEMENTS          191 

of  the  metal  by  the  strong  acid.  Owing  to  the 
activity  of  nitric  acid  in  combining  with  metals, 
older  chemists  named  it  aqua  fortis,  or  strong 
liquid.  The  action  of  the  acid  with  the  metals 
forms  nitrates,  or  oxides. 

Nitrogen  forms  five  compounds  with  oxygen,  but 
the  only  one  popularly  known  is  the  laughing  gas, 
nitrous  oxide,  already  spoken  of. 

PHOSPHORUS 

Phosphorus,  the  second  number  of  the  nitrogen 
group,  is  known  to  us  mainly  through  the  occur- 
rence of  phosphorus  in  nature,  and  compounds  of 
phosphorus  are  found  in  the  brain,  nerves,  and 
bones  of  animals.  Like  sulphur,  phosphorus  is 
allotropic,  existing  in  three  forms,  yellow,  red,  and 
black.  The  yellow  phosphorus  is  not  unlike  wax, 
though  it  becomes  brittle  when  cooled.  It  readily 
takes  fire  in  air  at  a  temperature  of  34  C.,  and  often 
at  a  lower  temperature  than  this  will  give  off  white 
fumes.  As  is  generally  known,  phosphorus,  slightly 
dampened,  glows  with  a  bright  yellow  light,  as 
may  be  seen  by  slightly  moistening  and  rubbing 
the  head  of  an  old-fashioned  match  in  a  dark  room. 
Pure  phosphorus,  owing  to  its  readiness  to  take 


192          THE    METALLIC    ELEMENTS 

fire,  has  to  be  kept  under  water,  and  must  never  be 
handled  in  the  air.  The  red  phosphorus  is  made 
by  heating  the  ordinary  form  in  a  closed  vessel. 


i  t        n 

MANUFACTUBE  OF  PHOSPHORUS 

R,  R,  R,  are  the  retorts  into  which  the  mixture  of  charcoal 
and  phosphorus  compounds  are  put;  F  is  the  furnace,  and  W,  W, 
the  water  tanks  where  the  vaporized  phosphorus  is  condensed. 

The  black  may  be  prepared  by  dissolving  red  phos- 
phorus in  melted  lead,  and  then  allowing  it  to  crys- 
tallize as  it  cools. 

Phosphorus  is  used  mainly  in  the  manufacture 
of  matches,  and  also  in  poisons  for  destroying  ani- 


THE    METALLIC    ELEMENTS          193 

mals.  While  the  yellow  phosphorus  is  used  for 
the  old-fashioned  friction  matches,  the  safety  match 
also  uses  red  phosphorus  in  the  prepared  surface 
upon  which  the  matches  are  to  be  struck.  Since 
phosphates  are  found  in  plants,  especially  in  the 
fruits  and  seeds,  vegetation  is  constantly  using  up 
the  phosphorus  in  the  soil,  and  this  must  be  re- 
placed if  the  land  is  to  be  kept  fertile,  by  com- 
pounds containing  phosphorus. 


CHAPTER   XII 

SOME  OTHER  METALLIC  ELEMENTS 

SODIUM  and  potassium,  together  with  three  rare 
elements,  lithium,  rubidium,  and  caesium,  are  usu- 
ally classified  together,  and  though  they  have  the 
character  of  metals,  they  seem  to  differ  from  other 
metals  in  possessing  strong  alkaline  properties. 

SODIUM 

Sodium,  the  first  of  these,  for  which  the  symbol  is 
Na,  from  the  Latin  name  natrium,  is  found  most 
abundantly  in  common  salt,  sodium  chloride,  and 
in  a  nitrate,  though  the  carbonate  also  is  common. 
Something  over  two  per  cent,  of  the  earth's  crust 
is  composed  of  sodium,  which  is  about  as  abundant 
as  aluminium.  Sodium,  pure,  is  a  silver-white 
metal,  so  soft  that  it  is  like  wax,  and  can  be 
moulded  in  the  fingers,  or  readily  cut.  It  is  a  trifle 
lighter  than  water,  and  melts  just  below  the  boil- 
ing point  of  water.  At  a  slightly  higher  tempera- 
ture, it  burns  with  a  brilliant  yellow  flame,  which 

195 


196          THE    METALLIC    ELEMENTS 

is  characteristic  of  all  the  sodium  compounds. 
To  keep  it  from  tarnishing,  it  is  ordinarily  im- 
mersed in  kerosene,  or  some  other  liquid  free  from 
water — with  which  sodium  will  combine  by  decom- 
posing the  water  and  freeing  the  hydrogen,  while 
it  forms  two  oxides,  Na2O  and  Na2O2.  When  put 
into  chlorine,  sodium  combines  with  it,  forming 
sodium  chloride,  or  common  salt,  and  by  this 
method  Sir  Humphry  Davy  proved  the  composition 
of  salt. 

This  compound,  sodium  chloride,  NaCl,  is  found 
almost  universally,  being  largely  produced  wher- 
ever sea  water  is  evaporated,  naturally  or  arti- 
ficially. The  freezing  of  sea  water  excludes  the 
salt  from  the  ice,  and  the  remaining  thick  solution 
of  salt  can  be  evaporated  by  heat.  Natural  de- 
posits of  salt,  known  as  "  rock  salt,"  are  found  in 
many  countries,  and  in  these  the  salt  is  mined  or 
used  impure  for  curing  meat  and  preserving  leather. 
Water  will  dissolve  about  one-third  of  its  own 
weight  of  salt,  or  more,  and  when  the  water  is 
allowed  to  evaporate,  the  salt  crystallizes  out  in 
cubes.  Common  salt  often  contains  chloride  of 
magnesium,  which  attracts  moisture,  and  in  pre- 
paring table  salt,  this  is  removed. 


THE    METALLIC    ELEMENTS 


197 


Sodium  hydroxide  (NaOH)  is  used  in  the  manu- 
facturing of  soap,  in  paper  pulp,  and  in  many 
chemical  industries.  Its  common  name  is  caustic 
soda.  Sodium  peroxide  (Na2O2)  contains  one 
more  atom  of  oxygen,  and  is  used  commercially 


APPAEATUS  FOB  THE  MANUFACTURE  OF  SODIUM  BY  THE  ELEC- 
TROLYSIS OF  SODIUM  HYDRONIDE 

The  body  of  the  steel  cylinder  rests  within  a  heated  flue. 
Hence  the  sodium  hydronide  is  solid  in  the  neck,  and  serves  to 
protect  the  joint  made  by  the  iron  cathode,  C,  and  the  crucible. 
A,  A,  is  the  iron  anode.  A  collecting  pot,  P,  dips  into  the  molten 
caustic  soda.  As  the  electrolysis  proceeds,  the  sodium  formed 
at  C  collects  in  P,  and  a  wire  gauze,  G,  G,  keeps  it  from  mixing 
with  the  caustic  soda.  The  sodium  is  ladled  out  at  intervals 
from  P.  The  hydrogen,  which  is  liberated,  accumulates,  also  in 
P,  and  prevents  the  sodium  from  oxidizing. 

for   bleaching   and   oxidizing.     There   is   also  a 
sodium  oxide.     One  of  the  most  important  com- 


198          THE    METALLIC    ELEMENTS 

pounds  of  sodium  is  the  sodium  carbonate 
(Na2CO3),  which  was  formerly  made  by  the  burn- 
ing of  seaweed,  but  is  now  prepared  from  the  chlo- 
ride. The  carbonate  is  often  called  soda,  or  sim- 
ply "alkali."  It  is  the  compound  known  as  wash- 
ing-soda. It  is  used  in  making  soap  and  in  glass 
manufactures,  and  in  preparing  other  sodium 
compounds. 

The  bicarbonate  of  soda  (HNaCO3),  the  white 
powder  commonly  known  as  cooking  soda,  or  bak- 
ing soda,  is  less  soluble  in  water  than  the  ordinary 
carbonate.  When  mixed  with  cream  of  tartar,  the 
combination  of  the  two  sets  free  carbon  dioxide, 
and  this  gas  raises  bread  or  cake  dough  by  forcing 
its  way  into  the  paste.  The  name  saleratus  is  some- 
times given  to  baking  soda  because  of  this  property, 
since  the  word  means  the  aerating  salt.  Seidlitz 
powders  or  Rochelle  salts  owe  their  effervescence 
to  the  same  sort  of  combination,  one  of  the  powders 
used  being  soda  bicarbonate.  In  medicine  the  same 
compound  is  often  used  for  indigestion,  to  counter- 
act acidity. 

Sodium  sulphate  (Na2SO4),  a  white  solid,  dis- 
solves readily  in  water,  and  crystallizes  on  evapora- 
tion into  Glaubers  salt,  used  in  glass-making,  in 


THE    METALLIC    ELEMENTS          199 

dyeing,  and  also,  when  purified,  as  a  medicine. 
Sodium  nitrate  is  found  in  Chili,  and  is  useful  as 
a  fertilizer  and  in  the  manufacture  of  nitric  acid 
and  potassium  nitrate.  It  is  known  as  Chili  salt- 
peter, and  is  used  in  making  blasting  powder,  but 
makes  too  explosive  a  compound  for  use  as  gun- 
powder. 

Borax  is  sodium  borate,  and  occurs  in  the  waters 
of  certain  lakes  in  Asia,  from  which  it  is  obtained 
by  evaporation.  It  is  also  found  in  California,  in 
solution,  and  can  also  be  extracted  from  compounds 
with  calcium  and  manganese.  It  possesses  valu- 
able antiseptic  properties,  is  used  as  a  food  preserv- 
ative, and,  owing  to  its  property  of  dissolving  many 
of  the  oxides,  is  used  as  a  flux  in  blow-pipe  analysis, 
as  is  mentioned  below  in  speaking  of  boron.  There 
are  many  other  compounds  of  sodium,  but  these  are 
the  most  important. 

POTASSIUM 

Potassium  (K)  is  nearly  as  abundant  as  sodium, 
occurring  as  a  compound  in  many  plants,  trees,  and 
animal  organisms.  It  is  found  as  a  nitrate  in  the 
soil  of  Ceylon  and  Bengal.  Combined  with  silica, 
it  occurs  in  feldspar  and  mica.  Salts  of  potassium 


200         THE    METALLIC    ELEMENTS 

are  contained  in  all  soils.  Originally,  potassium 
was  extracted  in  the  form  of  potash  from  ashes 
obtained  by  burning  wood,  leaves,  and  so  on,  these 
ashes  being  treated  with  water,  and  the  solution 
evaporated,  leaving  what  were  known  as  potashes. 
It  is  now  obtained  by  electrolysis  from  potassium 
hydroxide.  It  is  a  soft,  white  metal,  much  like 
sodium,  slightly  lighter,  but  ordinarily  covered  with 
a  greyish  coating,  owing  to  the  action  of  oxygen 
upon  it.  It  melts  far  below  the  boiling  point  of 
water,  and  burns  with  a  violet  flame,  which  gives 
the  test  for  its  presence  in  compounds.  Placed 
upon  water,  it  takes  fire,  just  as  sodium  does,  and 
burns  even  more  fiercely,  giving  a  violet  flame, 
forming  the  hydroxide,  and  releasing  hydrogen. 

Its  compounds  closely  resemble  those  of  sodium, 
though  it  combines  even  more  readily.  The  pure 
metal  has  no  commercial  uses,  is  expensive  to  pre- 
pare, and  is  only  a  chemical  curiosity.  An  impor- 
tant compound  is  the  potassium  hydroxide,  or  caus- 
tic potash  (KOH).  It  is  employed  in  surgery  as 
an  active  caustic  to  destroy  the  skin.  It  is  an 
alkali  of  great  strength,  readily  soluble  in  water, 
able  to  neutralize  acids,  and  decomposes  many 
metallic  solutions.  The  nitrate  of  potassium  is 


THE    METALLIC    ELEMENTS         201 

saltpetre,  or  nitre,  found  in  the  soil  of  many  warm 
countries.  It  is  a  white,  soluble  solid,  with  a  salty, 
cooling  taste,  giving  up  oxygen  readily,  especially 
to  charcoal  and  sulphur,  which  property  renders 
it  useful  in  making  gunpowder,  explosives,  and  in 
chemical  compounds.  Gunpowder  often  contains 
as  much  as  seventy-five  per  cent,  of  saltpetre,  which 
combines  with  the  oxygen  to  form  expanding  gases 
that  give  the  force  to  gunpowder  explosion. 

Potassium  chlorate  is  familiar  as  a  remedy  for 
sore  throat.  Its  value  consists  in  its  readiness  to 
part  with  oxygen,  and  it  is  likewise  used  in  the 
preparation  of  fireworks.  The  carbonate  of  potas- 
sium is  sometimes  called  potash,  or,  when  purified, 
pearlash,  and  enters  into  the  making  of  glass,  soap, 
and  other  potassium  compounds. 

Bromide  of  potassium  is  familiar  in  medicine, 
being  used  as  a  sedative,  and  also  in  photography 
as  a  means  of  slowing  the  action  of  developers. 
Potassium  cyanide  is  often  employed  in  extracting 
gold,  particularly  in  Africa,  and  also  is  used  with 
other  cyanides  in  electroplating.  Potassium  sul- 
phate is  useful  as  a  fertilizer  and  in  preparing 
alum. 

As  a  rule,  the  compounds  of  sodium  are  cheaper 


202          THE    METALLIC    ELEMENTS 

than  the  similar  compounds  with  potassium,  and 
are  therefore  apt  to  replace  them  commercially 
wherever  that  is  possible.  Now  and  then  the  po- 
tassium compound  will  have  certain  qualities  that 
fit  it  to  a  special  use,  and  thus  overcome  its  extra 
expense  as  compared  with  sodium.  An  advantage 
in  the  case  of  potassium  is  the  fact  that  its  com- 
pounds are  often  more  energetic  in  combination. 

LITHIUM,  RUBIDIUM  AND  CAESIUM 

The  three  remaining  metals  of  this  group  are  not 
only  rare,  but  are  of  little  use  commercially. 
Lithium  is  the  lightest  of  all  the  metal  elements. 
Its  compounds  are  widely  distributed,  but  found  in 
small  quantities.  Its  action  is  like  that  of  sodium 
toward  water  and  oxygen,  and  it  unites  vigorously 
with  hydrogen,  nitrogen,  and  oxygen.  Many  of  its 
compounds  are  almost  insoluble,  and  in  this  respect 
lithium  is  more  like  magnesium  than  the  alkali 
metals.  The  carbonate  of  lithium  and  some  other 
compounds  are  supposed  to  be  beneficial  in  certain 
rheumatic  disorders.  Lithium  tends  to  give  flame 
a  bright  red  color.  Kubidium  and  caBsium  are  two 
metals  that  were  discovered  by  the  use  of  the  spec- 
troscope, and  received  their  name  from  the  color 


THE    METALLIC    ELEMENTS         203 

of  their  characteristic  lines,  rubidium  giving  red, 
and  caesium  blue  lines.  They  both  form  compounds 
much  like  those  of  potassium,  and  have  somewhat 
similar  properties. 

CALCIUM 

The  pure  metal  calcium  (Ca)  belongs  to  a  class 
known  as  "  metals  of  the  alkaline  earths,"  being 
grouped  with  strontium  and  barium.  While  these 
metals  are  exceedingly  rare,  compounds  of  calcium 
are  exceedingly  plentiful,  and  the  compounds  of 
the  others  are  useful  and  numerous.  The  metal, 
calcium,  has  to  be  preserved  under  naphtha, 
and  is  only  a  curiosity.  Calcium,  however,  is 
found  abundantly  in  marble,  limestone,  chalk, 
in  shells,  bones,  coral,  etc.  The  carbonate,  or  cal- 
cide,  is  the  compound  that  forms  these  substances, 
and  is  found  pure  in  the  form  of  Iceland  spar. 
Calcium  sulphate  is  known  as  gypsum,  alabaster, 
and  selenite.  Limestone  is  found  abundantly  all 
over  the  world,  and  differs  greatly  in  hardness. 
Water  containing  carbon  dioxide  dissolves  lime- 
stone, and  as  such  water  is  very  frequent  in  na- 
ture, there  are  innumerable  formations  depend- 
ing upon  this  property.  The  water  frequently  de- 


204          THE    METALLIC    ELEMENTS 

posits  the  limestone  again,  forming  the  great  stalac- 
tites and  stalagmites.     This  accounts  for  the  for- 


LIME  KILN 

mation  of  the  great  Mammoth  Cave  in  Kentucky, 
and  the  Luray  Cave,  in  Virginia.  From  limestone 
are  prepared  limes  and  cements  used  in  building. 
Forms  of  rock  that  owe  their  formation  to  shells 
are  very  numerous.  Examples  are  the  coquina  of 
Florida,  and  the  chalk  cliffs  of  England.  Lime- 
stone is  exceedingly  useful  in  the  iron  industry, 


From  Stenograph,  Copyright,  by  Underwood  <fr   VnAerwooA,  Nnw  York. 

STALAuMlTE    FORMATION    OF    LIMESTONE    FOUND    IN    CAVES. 


THE    METALLIC    ELEMENTS          205 

being  used  to  extract  impurities  from  the  melted 
iron. 

Lime  is  calcium  oxide  (CaO).  Lime  is  obtained 
by  burning  limestone  mixed  with  charcoal.  It  is  a 
white  solid,  soluble  in  water.  It  resists  heat,  and 
is  hardly  at  all  fusible.  This  makes  it  useful  for 
crucibles  in  which  even  platinum  can  be  melted. 
Quicklime,  when  heated  by  the  oxy-hydrogen  flame, 
emits  an  intense  light,  formerly  called  the  "  Drum- 
mond,"  but  now  the  "  calcium  light." 

The  uses  of  lime  are  exceedingly  important  and 
numerous.  Besides  forming  mortars  and  cements, 
it  gives  us  calcium  carbide  ( from  which  acetylene 
gas  is  derived),  purifies  sugar,  makes  bleaching 
powders,  is  used  in  dyeing  and  bleaching  of  cloth- 
ing, is  used  as  a  disinfectant,  and  enters  into  many 
fertilizers.  Limestone  with  clay  forms  hydraulic 
cement,  which  hardens  in  contact  with  water.  Such 
cements  as  Portland  and  Rosendale  are  varieties. 

Slaked  lime  is  formed  by  adding  water  to  lime, 
making  calcium  hydroxide  Ca  (OH)2,  and  when  it 
is  added  to  water  till  it  forms  a  clear  solution,  the 
solution  is  called  "  lime  water."  When  diffused 
through  the  water,  it  forms  the  solution  known  as 
milk  of  lime,  or  "  whitewash." 


206          THE    METALLIC    ELEMENTS 

Slaked  lime  is  used  in  purifying  coal  gas,  in  tan- 
ning, dyeing,  and  bleaching.  Calcium  chloride  is  a 
white  solid,  and  has  the  greatest  affinity  for  water. 
Hence  it  is  used  as  a  drying  agent,  as  it  absorbs 
water  from  gases  or  solids.  It  melts  with  great 
readiness,  absorbing  heat,  and  is  thus  a  powerful 
refrigerating  agent.  A  mixture  with  snow  will 
freeze  even  mercury. 

Calcic  sulphate  is  gypsum,  of  which  we  have  al- 
ready spoken,  under  "  Sulphur."  Water  which 
holds  gypsum  in  solution  is  said  to  be  permanently 
hard,  and  is  particularly  troublesome  when  used 
in  steam-boilers  or  in  cooking  or  washing.  Gyp- 
sum is  most  useful  in  the  preparation  of  plaster  of 
paris  and  stucco.  It  also  is  useful  in  forming  terra 
alba,  used  to  give  weight  to  paper.  Crude  gypsum 
is  a  fertilizer. 

BORON 

Boron  has  certain  likenesses  to  the  hydrogen 
family,  and  may  therefore  be  considered  with  them, 
though  it  also  differs  from  them  in  some  respects. 

When  pure,  boron  is  a  greenish-brown  powder, 
which  burns  when  heated  in  the  air,  but  has  no 
odor  or  taste.  It  forms  with  carbon  a  carbon  bo- 
ride,  which  is  said  to  be  harder  than  the  diamond. 


THE    METALLIC    ELEMENTS         207 

In  nature  it  is  found  in  the  form  of  boric  acid  or 
in  its  salts.  A  familiar  salt  is  the  sodium  salt, 
known  by  the  common  name,  borax.  The  boric 
acid  occurs  in  large  quantities  in  some  localities, 
being  found  in  jets  of  steam  issuing  from  the  earth. 
These  jets  can  be  condensed  in  tanks  of  water, 
and  when  the  water  is  evaporated  the  acid  forms 
crystals.  Borax  contains  a  large  amount  of  water, 
as  will  be  seen  from  its  formula  (Na2B4O7. 10H2O) . 
Borax  is  often  used  in  the  laboratory  to  dissolve 
substances  for  examination.  The  borax  is  melted 
into  a  bead  on  the  end  of  a  piece  of  platinum  wire. 
When  the  bead  is  colored  by  the  substance  to  be 
examined,  and  then  is  held  in  the  flame  of  a  blow- 
pipe, the  changes  of  color,  and  so  on,  enable  the 
chemist  to  tell  what  has  been  added  to  the  bead. 

Borax  is  a  white  crystalline  solid,  used  in  the 
manufacture  of  enamel  and  glass,  and  for  making 
artificial  precious  stones.  It  is  a  preservative  for 
canned  goods,  and  is  especially  good  as  a  cleansing 
agent  in  laundries,  and  is  often  combined  with  soap. 
Having  the  power  of  dissolving  oxides,  borax  is 
placed  on  metal  surfaces  meant  to  be  soldered  and 
removes  any  oxide,  leaving  the  metal  clean.  It  is 
also  used  in  calico  printing,  in  dyeing,  and  enters 


208         THE    METALLIC    ELEMENTS 

into  certain  ointments  in  medicine.  Boric  acid 
(H3BO3)  is  used  in  much  the  same  way.  It  will 
be  seen  that  this  does  not  contain  the  sodium  found 
in  borax. 

SILICON 

Silicon  is  sometimes  classed  with  carbon,  and 
sometimes  with  boron,  but  as  carbon  compounds 
are  so  complicated,  they  are  best  studied  by  them- 
selves, and  the  description  of  silicon  may  well  fol- 
low that  of  boron.  So  abundant  are  the  silicon 
compounds  that  they  make  up  perhaps  one-fourth 
of  the  earth's  crust;  and  silicon  is  the  most  impor- 
tant mineral  element,  as  carbon  is  the  most  impor- 
tant in  organic  life.  The  commonest  compounds 
are  silicon  dioxide  (SiO2)  and  silicates.  An  exam- 
ple of  the  family  is  quartz,  or  sand.  The  silicates 
are  usually  found  as  rocks.  Silicon  does  not  occur 
free  in  nature.  The  dioxide,  called  also  silica,  oc- 
curs in  a  great  number  of  varieties  that  differ  in 
form  and  color  according  to  the  other  substances 
contained  in  them  or  to  their  method  of  formation. 
Kock  crystal  and  amethyst  are  crystalline  silica. 
Other  varieties  are  chalcedony,  carnelian,  jasper, 
flint,  and  so  on.  Silica  combined  with  water  makes 
the  opal.  What  is  known  as  petrified  wood  is 


THE    METALLIC    ELEMENTS         209 

formed  by  the  washing  away  of  woody  fibre  and  its 
replacing  by  silica.  Quartz  cannot  be  melted  ex- 
cept in  an  electric  furnace  or  the  hydrogen  flame, 
but  when  fused,  it  may  be  drawn  out  into  delicate 
threads,  which  are  so  fine  as  to  be  used  in  scientific 
instruments,  or  may  be  used  like  a  glass. 

Silica  is  very  common  in  plants,  and  is  used  in 
their  construction  to  give  them  stiffness  and  to 
strengthen  joints.  Thus  the  coating  of  bamboo 
and  certain  grasses,  as  well  as  the  quills  of  feathers 
and  other  such  substances,  are  stiffened  by  silica. 
Silicates  are  the  result  of  the  action  of  some  acid 
containing  silicon  upon  various  bases.  They  make 
up  a  large  part  of  the  earth's  crust,  and  form  many 
common  rocks  and  minerals,  among  which  we  may 
mention  mica,  feldspar,  clay,  slate,  and  talc.  Sili- 
cates of  sodium,  or  potassium,  dissolve  in  water, 
and  the  solutions  are  known  as  water  glass,  being 
used  in  yellow  soaps,  in  cements,  and  in  fire-proof- 
ing clothing  and  wood.  It  will  be  remembered  that 
in  speaking  of  carborundum  we  said  that  it  was  a 
silicon  carbide,  CS. 

One  of  the  most  important  compounds  we  owe  to 
silicon  is  glass,  which  is  a  mixture  of  certain  sili- 
cates, especially  of  potassium  or  sodium.  There 


210          THE    METALLIC    ELEMENTS 

are  a  great  number  of  mixtures  that  will  form 
glasses  for  various  purposes,  from  the  peculiar  mix- 
tures used  in  manufacturing  photographic  lenses 
to  those  used  in  making  glass  objects  such  as  ordi- 
nary bottles.  Colored  glasses  are  made  by  adding 
substances  to  the  mixture  when  melted.  Thus  ruby 
glass  depends  for  its  coloring  upon  gold  or  copper. 
Yellow  may  be  made  by  adding  charcoal,  sulphur, 
or  silver;  and  other  substances  may  be  used  ac- 
cording to  the  color  desired. 

Silicon  is,  next  to  oxygen,  the  most  abundant  of 
all  the  elements,  since  it  is  found  not  only  in  the 
rocks  but  also  in  all  forms  of  clay.  There  is  a 
certain  likeness  in  many  of  the  compounds  formed 
by  silicon  and  by  carbon,  the  same  number  of  ele- 
ments of  each  combining  with  a  like  number  of 
atoms  of  certain  other  elements. 

The  first  glass  was  made  with  salts  of  potassium 
mixed  with  the  silica;  and  this  glass,  known  as 
Bohemian  glass,  is  not  so  easily  melted  as  that 
made  with  sodium.  By  mixing  lead  oxide  with 
silica  and  potash,  plate  glass  is  made.  This  is  soft 
and  easily  worked,  but  its  high  power  of  refracting 
makes  it  useful  for  lenses  generally.  Very  pure 
flint  glass  is  the  basis  from  which  artificial  precious 


THE    METALLIC    ELEMENTS         211 

stones  are  made.  Ordinary  glass,  known  as  crown, 
is  a  silicate  of  sodium  and  lime.  The  cheaper 
grades  of  glass  contain  an  iron  oxide  that  gives 
them  a  greenish  color.  Glass  has  to  be  carefully 
and  slowly  cooled,  or  annealed,  in  order  that  it 
may  not  be  too  brittle. 


CHAPTER   XIII 

CARBON  AND  ITS  STRANGE  COMPOUNDS 

WHILE  it  is  true  that  we  have  already  treated 
briefly  carbon  and  some  of  its  combinations,  yet 
since  carbon  forms  the  foundation  of  all  the  most 
important  compounds  that  enter  into  living  organ- 
isms, and  also  of  most  substances  that  are  derived 
from  them,  its  chemical  story  is  so  wide  and  varied 
that  it  has  long  been  customary  to  divide  all  chem- 
istry into  two  great  branches,  the  second  of  which 
is  devoted  almost  exclusively  to  carbon  compounds. 

The  reason  why  carbon  is  thus  distinguished  from 
other  elements  is  twofold :  first,  as  we  have  said,  it 
enters  into  substances  that  being  in,  or  derived 
from,  living  creatures  or  organisms,  are  conven- 
iently considered  by  themselves ;  secondly,  owing  to 
its  nature,  carbon  forms  an  almost  endless  variety 
of  compounds.  To  explain  this  second  feature  we 
must  bear  in  mind  the  subject  of  valency.  In  dis- 
cussing the  table  classifying  elements  by  the  peri- 
odic system,  we  shall  consider  this  subject  and 
show  how  elements  vary  in  regard  to  it.  Carbon 

213 


214      CARBON   AND    ITS   COMPOUNDS 

ordinarily  has  the  valency  4;  that  is,  it  is  capable 
of  replacing  four  atoms  of  hydrogen  (or  other 
monad).*  It  is  also  able  to  remain  in  combina- 
tion with  any  four  monads,  two  dyads,  one  monad 
and  a  triad,  and  so  on.  This  alone  would  produce 
a  multiplicity  of  compounds,  but  carbon  also  has 
the  power,  like  some  other  elements,  of  forming 
combinations  in  which  atoms  of  carbon  are  them- 
selves combined,  thus  making  substances  in  which 
atoms  of  carbon  are  combined  more  or  less  with 
one  another.  Thus  if  we  suppose  two  carbon  atoms 
joined,  they  may  hold  many  more  than  the  equiv- 
alent of  four  monads  in  combination. 

Exactly  how  atoms  are  linked  together  in  com- 
pounds is  not  known,  but  it  is  usual  to  represent 
this  linking  as  if  the  element  had  as  many  links 
or  arms  of  attachment  as  it  has  valency.  Repre- 
sented thus,  the  carbon  atom  may  be  remembered  as 
a  circle  containing  the  letter  C,  and  with  the  four 

arms  of  a  cross  projecting  from  it,  thus :  H9^ 
or  (c)z  or    r@z    and  in  other  similar  ways. 

*An  element  of  a  valence  of  one,  is  called  a  monad;  of  two 
valences,  a  dyad;  three,  triad;  four,  a  tetrad;  five,  a  pentad; 
six,  a  hexad; — and  so  on,  using  the  Greek  numbers  to  form 
these  words,  just  as  in  Geometry  the  same  prefixes  are  used  in 
the  words:  triangle,  tetragon,  pentagon,  hexagon,  heptagon. 


CARBON   AND    ITS   COMPOUNDS      215 

Though  we  are  not  to  think  of  this  as  repre- 
senting the  truth,  yet  it  helps  us  to  follow  the  link- 
ing of  carbon,  and  it  is  readily  seen  that  if  these 
atoms  with  their  four  arms  may  be  joined  in  a 
chain,  or  a  ring,  we  may  have  compounds  with 
almost  any  amount  of  valency,  that  is,  that  will 
admit  of  putting  together  elements  in  endless  sets 
of  systems,  for  to  the  carbon  arms  may  be  attached 
other  elements,  each  of  which  has  arms  of  its  own, 
and  thus  the  chain  be  continued  in  all  four  direc- 
tions. 

Nor  is  all  this  a  mere  matter  of  "  chemistry  on 
paper."  Carbon  atoms  do  admit  of  such  com- 
pounds, and  they  are  known  in  nearly  unlimited 
number.  It  is  true  that  some  of  them  may  be 
thrown  into  classes,  owing  to  the  resemblance  of 
the  general  plan  upon  which  they  are  built  up. 
But  the  substitution  of  a  single  atom  or  set  of  atoms 
will  change  a  compound  into  a  new  substance  with 
new  qualities. 

The  chief  elements  that  enter  into  all  organisms 
are  carbon,  hydrogen,  and  oxygen,  and  in  a  partic- 
ular class — the  animal  substances — nitrogen  exists 
also.  The  combinations  of  hydrogen  with  carbon, 
alone,  are  the  foundation  for  an  enormous  class 


216      CAKBON    AND    ITS   COMPOUNDS 

of  substances  known  as  the  "  hydrocarbons,"  and 
these  differ  greatly,  being  modified  by  the  amount 
of  oxygen  present.  When  to  these  three  elements 
we  add  nitrogen,  to  get  the  nitrogenous  substances, 
we  have  another  large  class,  and  by  adding  other 
elements  to  the  members  of  these  great  classes  we 
vary  them  into  substances  that  form  the  material 
out  of  which  all  organized  nature  is  built  up. 

In  animals  and  plants,  all  these  substances  are 
in  a  constant  state  of  change.  Atoms  are  ex- 
changed, combinations  are  made  or  broken  up, 
substances  are  destroyed  in  one  form  to  reap- 
pear in  several  others,  and  thus  the  whole  great 
mass  of  changes  which  constitute  life  are  car- 
ried on.  Affecting  these  changes  more  or  less 
in  organized  life  are  the  great  agencies,  heat, 
light,  and  electricity,  the  action  of  which  must  be 
studied  in  order  to  follow  the  chemical  changes 
among  these  compounds  so  universally  present. 

In  the  early  days  of  chemistry,  it  was  believed 
that  many  of  these  "  organic  compounds "  owed 
their  formation  to  some  unknown  principle  acting 
in  living  things,  and  therefore  could  not  be  pre- 
pared except  by  nature — that  is,  not  artificially. 
But  in  1828  the  chemist  Wbhler  succeeded  in  pre- 


Repi-uluceilfi-oni  "  Youn/j'a  El-mentanj  principles  of  Chemistry,"  by  permission  of  I) .  AppMoii  it  Company. 

FBIEDRICII  WOHLER 
B.  Germany,  1800.     D.  1882. 


CARBON   AND    ITS   COMPOUNDS      217 

paring  the  compound  urea,  till  then  found  only  in 
animals,  and  never  made  from  inorganic  substances. 
This  disproved  the  belief  that  all  such  substances 
were  necessarily  beyond  the  reach  of  the  chemist. 
Experiments  to  prepare  other  organic  compounds 
followed.  Many  were  successful,  and  as  the  laws 
of  their  making  were  found  out,  it  came  to  be  be- 
lieved that  these  compounds  were  subject  to  the 
same  general  chemical  laws  as  the  others ;  and  that 
is  the  belief  to-day.  It  was  soon  found  that  the 
complexity  of  these  substances  was  due  rather  to 
the  varied  ways  in  which  a  few  elements  were 
joined,  than  to  the  number  of  elements  entering 
into  them. 

Besides  the  four  elements  already  mentioned, 
sulphur  and  phosphorus  were  those  oftenest  found 
in  organic  compounds.  The  cause  of  the  complex- 
ity came,  as  already  suggested,  from  the  power  of 
the  carbon  atoms  to  unite  together;  the  fact  that 
new  atoms  may  be  simply  added,  or  may  replace 
others;  that  the  arrangement  of  the  atoms  in  car- 
bon compounds  may  be  varied,  even  when  the  same 
atoms  are  present;  and  also  to  the  circumstance 
that  in  the  carbon  compounds  radicals  frequently 
occur — the  radicals  being  atoms  combined  in 


218      CAKBON   AND    ITS    COMPOUNDS 

groups  that  often  remain  together,  even  when  their 
compounds  vary. 

It  will  be  seen  from  this  statement  that  only  the 
most  general  facts  concerning  these  compounds  can 
be  shown  in  this  book.  We  shall  therefore  say 
something  about  the  chief  classes  of  carbon  com- 
pounds, and  add  to  these  merely  a  mention  of  some 
of  the  commoner  substances  belonging  to  this 
branch  of  chemistry. 

Of  the  compounds  of  carbon  with  oxygen  we  have 
spoken  already  in  treating  carbon  among  the  ele- 
ments. The  important  ones  are  the  gases,  carbon 
monoxide  and  the  carbon  dioxide.  When  carbon  is 
combined  with  hydrogen,  three  important  gases  are 
produced.  These  have  the  formulas,  CH4,  known 
as  marsh  gas,  "  natural  gas,"  or  methane ;  C2H4, 
olefiant  gas,  or  ethylene;  and  C2H2,  or  acetylene 


gas.  By  looking  at  these  formulas  it  will  be  seen 
that  in  the  first,  carbon  is  linked  to  four  atoms  of 
hydrogen;  in  the  second  gas  the  two  carbon  atoms 
are  joined  to  one  another  by  two  links,  leaving  four 


CARBON   AND    ITS   COMPOUNDS      219 

links  for  the  four  hydrogen  atoms.  In  acetylene, 
the  carbon  is  so  joined  as  to  link  only  two  atoms  of 
hydrogen. 

Remembering  what  has  been  said  about  the  power 
of  carbon  to  make  new  compounds  by  change  of 
atoms,  we  shall  not  be  surprised  to  learn  how  these 
can  be  varied.  To  give  an  example  of  this — if  we 
imagine  one  of  the  H  atoms  in  methane  to  be  re- 
placed by  an  atom  of  oxygen,  to  which  the  hydrogen 
atom  is  again  attached,  we  shall  have  the  compound, 

methyl  alchol.  ** 

H— C— O— H 

H 

Methane  is  marsh  gas,  which  rises  from  marshes, 
and  is  found  in  coal  mines  under  the  name  "fire 
damp,"  and  comes  from  the  ground  in  "  natural 
gas"  regions.  The  second  compound  (C2H4)  is 
known  as  ethylene,  and  is  found  in  ordinary  il- 
luminating gas,  giving  the  light  a  yellowish  flame. 
The  acetylene  formerly  formed  in  distilling  wood 
or  coal,  is  now  prepared  by  combining  calcium  car- 
bide with  water,  as  in  acetylene  gas-generators.  It 
gives  an  extremely  brilliant  light  and  an  intense 
heat.  All  of  these,  prepared  in  various  ways,  are 
used  in  illuminating. 


220      CARBON   AND    ITS   COMPOUNDS 

ALCOHOLS 

We  have  spoken  of  methyl  alcohol.  It  is  one  of 
a  whole  class  of  compounds  named  "  alcohols,"  of 
which  spirit  alcohol  is  known  as  ethyl  alcohol,  and 
that  called  wood  alcohol  is  the  methyl  alcohol. 
They  are  made,  or  derived  from,  three  hydrocarbons 
called  methane,  ethane,  and  propane.  The  for- 
mulae for  these  three  are  CH4, 
C2H6,  and  C3H8.  There  is  an- 
other, C4H10,  called  butane.  It 
will  be  seen  on  examining 
these  formulaB  that  in  each  suc- 
ceeding case  there  is  one  more 
atom  of  carbon  and  two  more 
ACETYLENE  FLAME  of  hydrogen.  Thus  these  com- 
pounds are  looked  upon  as  a  regular  series,  and 
are  called  the  paraffin  series.  In  general,  they  are 
compounds  in  which  each  carbon  atom  has  been 
united  with  hydrogen  in  all  its  free  links. 

The  alcohols  in  general  are  formed  from  certain 
radicals  known  as  ethyl,  methyl,  and  propyl,  by 
replacing  a  hydrogen  atom  by  the  radical  hydroxyl 
(OH).  Thus  the  methane,  ethane,  and  so  on,  lack- 
ing the  hydrogen  atom,  give  us  radicals  ethyl, 
methyl,  and  so  on ;  and  when  the  missing  atom  of 
hydrogen  is  replaced  by  OH,  or  hydroxyl,  we  have 


CARBON   AND    ITS   COMPOUNDS      221 

the  series  of  alcohols.  Alcohol  in  Arabic  means 
"  the  spirit,"  and  these  compounds  are  named  from 
the  best  known  of  their  class,  the  ordinary  alcohol 
formed  from  wine  by  distillation. 

We  have  already  spoken  of  certain  hydroxides, 
as,  NaOH,  sodium  hydroxide,  and  KOH,  potassium 
hydroxide.  These  are  metallic  hydroxides,  and  it 
will  be  seen  that  if  we  suppose  the  metals  to  be  re- 
placed by  the  ethyl  and  methyl  radicals,  we  shall 
have  these  transformed  into  the  similar  alco- 
hols. 

Another  class  of  compounds,  known  as  "  alde- 
hydes/7 are  formed  when  alcohols  are  oxidized,  or, 
what  amounts  to  the  same  thing,  when  the  hydro- 
gen is  removed.  By  oxidizing,  the  hydrogen  unites 
with  O  to  form  H2O.  The  name,  aldehyde,  means 
alcohol  dehydrated,  or  deprived  of  water.  From 
aldehydes  are  prepared  formalin,  which  -is  used  in 
dye-stuffs,  as  a  preservative,  and  a  disinfectant. 
This  is  a  solution  of  formaldehyde,  a  gas  so  called 
because  with  oxygen  it  forms  an  acid  like  that 
secreted  by  ants  and  known  as  formic  acid.  By 
the  action  of  chlorine  upon  alcohol  is  formed 
chloral,  well  known  in  medicine.  This  may  be  de- 
composed by  an  alkali,  becoming  chloroform,  the 
formula  for  which  is  CHC13.  If  iodine  takes  the 


222      CARBON  AND  ITS   COMPOUNDS 

place  of  chlorine,  we  have  CHI3,  or  iodoform,  used 
in  surgery  as  a  dressing. 

Again  we  must  remind  the  reader  that  all  these 
compounds  may  be  greatly  varied  by  changes  and 
substitutions  of  elements  and  radicals. 

ETHERS 

Another  important  class  of  compounds  are  the 
ethers,  which  also  are  compounds  of  C,  H,  and  O. 
Ether  is  prepared  from  ethyl  alcohol  and  sulphuric 
acid,  the  result  of  the  operation  being  to  remove 
from  the  alcohol  the  atom  of  hydrogen  in  the  radi- 
cal hydroxyl;  that  is,  to  change  the  formula, 
C2H5OH,  into  (C2H5)2O.  This  slight  change  in 
chemical  composition  is  the  difference  between 
alcohol  and  ether.  The  ethers  dissolve  fats,  waxes, 
and  oils,  and  ordinary  ether  is  used  as  an  anes- 
thetic, as. is  well  known.  Here,  again,  there  is  a 
whole  group  of  ethers. 

ORGANIC  ACIDS 

Another  group  of  compounds  of  the  same  three 
elements  is  known  as  the  organic  acids,  the  com- 
monest of  which  is  acetic  acid,  found  in  vinegar  in 
a  diluted  form.  Acetic  acid  may  be  formed  by 
oxidizing  aldehyde,  which,  as  we  have  seen,  is 


CARBON  AND  ITS   COMPOUNDS      223 


formed  by  oxidizing  alcohol.  A  set  of  formulas 
taken  from  NewelFs  "  Descriptive  Chemistry "  * 
shows  very  clearly  the  relation  between  these  three 
and  ethane.  Wine  is  a  diluted  and  flavored  alcohol, 
and  is  well  known  to  turn  into  vinegar.  This  is 
caused  by  the  oxidizing  of  the  air,  which  unites 
with  alcohol,  forming  acetic  acid.  In  nature  this 
turning  is  caused  by  a  little  organism,  a  formation 
called  "  mother  of  vinegar,"  which  may  often  be 
seen,  for  example,  in  cider  that  has  stood  until  it 
has  turned  sour. 

The  action  of  acetic  acid  on  the  bases,  gives  rise 
to  the  salts  known  as  acetates,  used  in  dyeing  and 
making  pigments.  Paris  green  is  an  acetate  of  cop- 
per and  zinc. 

Among  other  organic  acids  are  "  oxalic,"  so 
named  from  the  plant,  oxalis;  lactic,  which  forms 
in  milk ;  malic,  tartaric,  and  citric,  in  fruits.  Many 
of  these  acids  are  in  common  use  in  manufactures, 


*           H 

H 

H 

H—  C—  H 

H-C—  (OH) 

(U 

O=C—  (OH) 

H—  C—  H 

H—  C—  H 

H—  C—  H 

H—  C—  H 

i 

A 

k 

1 

Ethane 

Ethyl 

Acetic 

Acetic 

Alcohol 

Aldehyde 

Acid 

224      CARBON  AND  ITS   COMPOUNDS 

and  even  in  the  home.  Cream  of  tartar  is  formed 
from  potassium  by  the  action  of  tartaric  acid,  and 
a  tartrate  of  potassium  and  antimony  is  "  tartar 
emetic,'*  used  in  medicine. 

It  is,  of  course,  impossible  to  enter  into  all  the 
compounds  that  owe  their  origin  to  these  organic 
acids,  and,  indeed,  the  slight  mention  of  a  few 
organic  compounds  here  made  is  designed  only  to 
give  the  reader  some  idea  of  the  way  in  which  these 
compounds  may  be  changed  by  addition  or  substi- 
tution. When  it  is  repeated  that  the  common 
groups  on  which  such  compounds  are  built  may  be 
doubled  or  tripled,  or  multiplied,  it  will  be  seen 
that  the  list  of  compounds  stretches  on  intermina- 
bly in  a  sort  of  endless  chain,  and  a  multitude  of 
these  chains  exist  derivable  from  methane,  ethane, 
propane,  butane,  and  pentane.  And  this  is  only 
one  of  the  carbon  series.  Even  the  larger  treatises 
on  chemistry  consider  only  the  more  important  and 
give  the  general  principles  that  explain  the  for- 
mulae of  all.  Thus  we  have  ethylenes,  propylenes, 
butylenes,  amylenes,  variations  of  the  alcohols,  of 
the  ethers,  and  so  on  throughout  nature.  Besides, 
we  have  studies  of  the  compounds,  soaps,  sugars, 
fats,  anilines — all  the  derivatives  of  coal-tar,  a 


CARBON  AND  ITS  COMPOUNDS      225 

chemistry  in  itself.  In  addition  to  these  are  a 
whole  set  of  complex  substances,  such  as  the  albu- 
mens, derived  from  the  vegetable  or  animal  king- 
dom. 

It  is  not  to  be  supposed  that  any  one  except  a 
professional  chemist  will  become  familiarly  ac- 
quainted with  these  higher  branches  of  chemistry. 
Even  these  men  confine  their  attention  to  a  few 
classes  of  substances  and  compounds,  and  refer  to 
books  for  detailed  knowledge  of  other  parts  of  the 
science.  The  general  reader  must  do  the  same  in 
a  larger  way.  After  having  become  generally  ac- 
quainted with  the  principles  of  chemistry,  he  will 
be  able,  by  the  use  of  reference  books, -to  inform 
himself  exactly  in  regard  to  matters  that  may 
excite  his  interest  or  be  necessary  in  his  work. 
Such  common  substances  as  butter,  milk,  olive  oil, 
and  soap,  are  chemically  exceedingly  complicated. 
In  butter,  for  example,  there  are  six  fats,  owing 
their  origin  to  six  different  acids.  The  study  of 
its  formation  is  only  possible  to  the  accomplished 
chemist.  Sugar,  in  chemistry,  also  covers  a  whole 
class  of  sweet  substances,  each  with  its  distinct 
constitution.  And  when  we  examine  the  make-up 
of  such  a  substance  as  coal  tar,  we  find  that  it  com- 


226      CARBON  AND  ITS  COMPOUNDS 

prises  a  complete  chemistry  in  itself — even  benzol, 
one  of  its  derivatives,  which  is  the  foundation  of 
many  derivatives,  gives  rise  to  an  endless  set  of 
compounds,  all  characterized  by  being  based  upon 
a  ring  of  the  carbon  atoms  linked  together. 

Then,  too,  there  is  a  whole  set  of  theories  to  ex- 
plain why  compounds  of  carbon  exist  in  so  many 
forms.  A  hint  of  this  may  be  given  by  saying 
that  the  carbon  atom  is  regarded  for  purposes  of 
analysis  as  a  triangular  pyramid  A  capable 
of  attachment  to  other  atoms  at  /  V\  each  of 
its  four  angles,  and  also  of  being  ^^-v  united 
with  pyramids  like  itself  at  various  angles  and 
surfaces.  Those  interested  will  find  the  subject 
discussed  under  the  heading  Stereo-chemistry,  in 
various  reference  books. 

Enough  has  been  said  to  show  the  reader  the 
endless  complexity  of  this  branch  of  chemistry, 
and  the  impossibility  of  doing  more  than  hinting 
at  its  depth. 


CHAPTER   XIV 

CHEMICAL  ACTION  AND  ENERGY 

THUS  far,  in  speaking  of  the  uniting  and  separa- 
tion of  elements  in  chemical  action,  we  have  thought 
chiefly  of  the  elements  or  compounds  as  they  ex- 
isted before  any  action  takes  place,  and  as  they 
exist  when  by  that  action  they  have  been  changed. 
But  the  most  important  matter  in  regard  to  chemi- 
cal action,  that  is,  the  nature  of  the  action  itself, 
deserves  to  be  especially  considered. 

The  union  or  disunion  of  elements  is  far  different 
from  every  mere  physical  mixture,  and  not  only  is 
it  different  in  its  results,  but  especially  in  its 
method  of  action.  Perhaps  the  most  striking  in- 
stance is  the  commonest — burning.  Though  we 
have  seen  that  burning  is  no  more  than  the  uniting 
of  oxygen  with  other  elements,  yet  we  can  all  appre- 
ciate how  violent  and  how  remarkable  this  action 
is.  In  the  early  ages  of  chemistry  the  savages  saw 
in  the  action  of  fire  something  so  mysterious  that 
fire  was  worshipped  as  a  god.  And  even  until 

227 


228    CHEMICAL   ACTION   AND    ENERGY 

late  in  the  world's  history,  fire,  on  account  of  its 
mystery  and  its  usefulness  to  mankind,  was  looked 
upon  as  holy  and  almost  divine.  This  will  serve 
to  illustrate  how  striking  chemical  action  may  be, 
and  the  same  is  further  shown  by  the  whole  his- 
tory of  what  was  known  as  magic.  The  properties 
of  phosphorus  and  of  sulphur,  the  power  of  acids 
to  dissolve  metals,  the  producing  of  colored  fires, 
the  transformation  of  solids  to  liquids  and  the  re- 
verse— all  these  chemical  changes  remained  for 
ages  the  stock  in  trade  of  priests,  magicians,  and 
wonder-workers. 

But  only  within  two  centuries  men  have  begun  to 
see  that  all  these  mysteries  have  laws  that  may  be 
studied  and  known,  and  that  the  knowledge  of 
these  laws  will  enable  us  to  change  mysterious  hap- 
penings to  facts  as  familiar  as  those  of  every-day 
life.  Chemical  changes  a  thousand  times  more 
wonderful  than  any  known  to  the  "  magicians  "  of 
old  are  now  practised  as  part  of  the  daily  routine 
in  a  hundred  great  factories.  Chemical  processes 
that  even  the  great  chemists  of  the  last  generation 
would  need  a  new  education  to  understand  are  now 
used  in  commercial  trades  and  supply  us  with  arti- 
cles of  daily  life. 


CHEMICAL   ACTION    AND    ENERGY    229 

All  this  has  come  from  a  study  of  the  effects  pro- 
duced by  chemical  action.  Those  effects  are  always 
related  to  the  production  or  the  using  up  of  some 
form  of  energy.  Usually  this  energy  is  evident  as 
heat — either  heat  given  out  or  heat  absorbed. 
When,  in  making  a  combination,  chemical  elements 
absorb  heat,  the  result  is  apt  to  be  unstable,  and 
if  the  combination  be  broken  up,  the  same  amount 
of  heat  taken  up  by  the  combining  will  be  liberated. 
On  the  other  hand,  certain  combinations  give  out 
heat  when  combining.  Combinations  so  formed  are 
apt  to  be  stable,  that  is,  not  easily  broken  up,  since 
they  must,  in  order  to  separate,  receive  from  some 
source  the  same  amount  of  heat  they  have  parted 
from  in  combining. 

This  will  be  better  understood  when  it  is  remem- 
bered that  we  know  heat  only  as  a  sign  of  motion, 
consequently  when  heat  is  given  out  in  the  making 
of  a  chemical  combination,  it  is  a  sign  that  the 
molecules  are  seeking  a  position  of  rest,  or  ceasing 
to  move  to  some  extent.  If  heat  is  absorbed,  they 
are,  on  the  contrary,  entering  into  a  state  of  greater 
motion,  and  since  they  may  part  again  with  this 
heat  and  return  to  their  state  of  greater  rest,  they 
are  naturally  in  a  more  unstable  condition. 


230     CHEMICAL   ACTION   AND    ENERGY 

This  can  be  readily  illustrated  when  we  think  of 
the  explosion  of  gunpowder.  When  oxygen  is  com- 
bined with  the  constituents  of  gunpowder,  much 
heat  is  given  out  by  the  oxidizing  of  the  elements, 
and  they  are  thereby  formed  into  new  compounds, 
mostly  gases,  which  have  parted  with  some  of  their 
capacity  for  motion  or  energy.  The  study  of  ex- 
plosives has  shown  that  they  are  compounds  which 
are  in  an  unstable  condition.  Their  combination, 
therefore,  produces  heat.  The  addition  of  an  acid 
to  a  base  is  an  example  of  a  combination  in  which 
heat  is  ordinarily  given  out,  and  a  stable  compound 
or  set  of  compounds  results. 

Sometimes  the  energy  appears  in  another  form 
than  heat.  Thus  the  combination  of  oxygen  with 
other  elements,  if  rapid  enough,  will  in  most  cases 
produce  light  as  well  as  heat.  In  the  electric  bat- 
tery the  action  of  an  acid  upon  a  metal,  which  is  a 
slower  oxidizing,  sets  free  the  form  of  energy 
known  as  electricity. 

Thus  every  chemical  compound  may  be  looked 
upon  as  not  only  a  change  in  the  condition  of  the 
substances  that  enter  into  it,  but  also  as  a  releas- 
ing or  a  taking  up  of  some  form  of  energy — either 
heat,  light,  or  electricity. 


CHEMICAL   ACTION    AND    ENERGY     231 

The  setting  free  of  these  is  more  or  less  familiar. 
We  have  come  to  expect  to  see  chemical  action  ac- 
companied by  heating,  by  light,  or  by  electricity, 
but  the  contrary — that  is,  taking  up  of  energy — is 
less  familiar.  But  only  a  little  reflection  will  make 
this  opposite  action  also  plain  to  us. 

If  light,  for  example,  is  allowed  to  fall  upon  one 
of  the  unstable  compounds  of  silver,  such  as  the 
bromide,  the  chloride,  or  iodide,  of  silver,  as  pre- 
pared in  a  photographic  film,  we  know  that  the 
effect  of  that  light  is  to  change  the  composition  of 
the  silver  compound — to  affect  it  in  such  a  manner 
that  when  we  apply  to  the  plate  a  chemical  that 
before  would  not  act  upon  it,  this  chemical  "  de- 
velops "  the  plate,  whereas  the  unexposed  plate 
would  not  be  affected  by  the  developer.  This  is 
an  instance  of  the  using  up  of  light  energy  in  be- 
ginning a  chemical  combination. 

The  using  of  heat  energy  is  more  readily  recog- 
nized. Again  we  cite  the  explosion  of  gunpowder, 
the  burning  of  a  charred  stick  in  oxygen,  or  the 
combining  of  hydrogen  and  oxygen  into  water  as 
soon  as  heat,  either  a  flame  or  an  electric  spark, 
is  applied  to  the  mixture.  The  instances  wherein 
electric  energy  is  absorbed  in  the  making  of  chemi- 


232    CHEMICAL   ACTION   AND    ENERGY 

cal  combinations  are  numberless.  The  most  famil- 
iar of  these  is  electro-plating.  In  this  chemical 
process  the  passing  of  electricity  through  a  solution 
causes  the  separation  of  compounds  in  solution,  and 
their  combination  in  new  forms  or  in  new  places. 
Of  late  years  many  methods  of  producing  ex- 
tremely low  or  extremely  high  temperatures  have 
been  discovered,  and  the  proofs  that  heat  plays  a 
most  important  part  in  all  chemical  action  have 
rapidly  accumulated.  When  subjected  to  tempera- 
tures hundreds  of  degrees  below  zero,  chemicals, 
which  at  ordinary  temperatures  combine  rapidly, 
seem  to  become  inert  and  have  no  action  upon  one 
another.  At  extremely  high  temperatures  the  op- 
posite is  seen — combinations  are  made  of  sub- 
stances that  ordinarily  can  be  mixed  or  brought 
into  close  contact  without  action.  To  give  a  mod- 
ern example,  acetylene  gas  is  produced  by  bringing 
calcium  carbide  into  contact  with  water.  But  this 
calcium  carbide  is  not  produced  simply  by  a  mix- 
ture of  carbon  and  lime  (calcium  oxide).  The 
chemical  combination  of  these  two  is  produced 
solely  by  the  high  temperature  to  which  they  are 
raised.  At  a  lower  temperature  they  show  no  dis- 
position to  unite.  Another  substance  due  to  the 


CHEMICAL   ACTION    AND    ENERGY     233 

high  temperature  produced  by  the  electric  furnace 
is  carborundum.  A  mixture  of  coke,  sawdust,  and 
sand,  on  being  heated,  results  in  a  combination  of 
the  silicon  and  the  carbon  into  silicon  carbide,  the 
chemical  name  for  carborundum.  This  is  a  sub- 
stance nearly  as  hard  as  the  diamond,  which  is 
used  for  whetstones  and  other  sharpening  appli- 


CAEBOBUNDUM  FUBNACE 

ances.  The  fact  that  this  can  be  chemically  made 
is  due  to  the  enormous  energy  obtained  from 
Niagara  Falls  and  converted  by  turbine  wheels  into 
electricity. 

ELECTROLYSIS 

The  separation  of  a  chemical  compound  into  its 
elements  by  means  of  a  current  of  electricity  dates 
back  into  the  eighteenth  century,  for  in  1789  two 
chemists,  having  sent  electric  discharges  through 


234     CHEMICAL   ACTION   AND    ENERGY 

water  in  a  tube,  found  that  a  mixture  of  gases  grad- 
ually gathered  in  the  upper  part  of  the  tube,  and 
that  when  accidentally  an  electric  spark  was  caused 
in  the  portion  of  the  tube  above  the  water — one 
of  the  wires  having  become  uncovered — these  gases 
disappeared  and  the  water  again  filled  the  tube. 
Study  of  this  experiment  led  these  chemists  to  be- 
lieve that  hydrogen  and  oxygen  had  been  separated 
from  the  water  and  then  united  again  into  water. 
In  order  to  obtain  even  a  small  quantity  of  these 
gases,  thousands  of  electric  discharges  were  neces- 
sary. 

Later  on,  when  the  Leyden  jar  with  its  strong 
charge  was  invented,  from  fifty  to  sixty  discharges 
of  electricity  through  a  solution  of  silver  nitrate 
were  enough  to  cause  a  visible  amount  of  the  metal 
silver  to  collect  on  one  of  the  wires,  the  negative 
electrode.  Then  the  current  was  reversed,  making 
the  other  wire  negative,  whereupon  the  silver  de- 
posit gradually  disappeared  from  the  first  wire  and 
appeared  on  the  other.  Meanwhile,  Volta  had  pro- 
duced his  electric  battery,  and  the  stronger  charges 
of  electricity  were  used  in  repeating  the  experiment 
of  decomposing  compounds.  With  a  stronger  bat- 
tery a  current  sent  through  river  water  between 


CHEMICAL   ACTION    AND    ENERGY    235 

brass  wires  produced  bubbles  that  came  in  a  fine 
stream  from  the  negative  wire.  To  the  astonish- 
ment of  the  experimenters  it  was  soon  found  out 
that  in  the  decomposing  of  water,  hydrogen  ap- 
peared at  one  wire  and  oxygen  at  the  other.  This 
was  in  1800,  and  in  the  same  year  the  experimenter 
succeeded  in  decomposing  a  solution  of  lead  acetate. 

Sir  Humphry  Davy  used  two  tubes  of  glass  to 
cover  the  two  separated  wires  and  thereby  was  able 
to  show  that  one  became  a  receiver  of  hydrogen 
and  the  other  of  oxygen,  and  that  these  two  gases 
appeared  in  the  same  proportion  in  which  they  ex- 
isted in  water.  There  were  many  attempts  made 
by  different  philosophers  to  explain  the  reason  for 
the  separation  of  the  elements  at  the  two  poles. 

The  work  of  Faraday  showed  that  there  was  an 
exact  relation  between  the  amount  of  electricity 
passing  through  the  solution  and  the  amounts  of 
the  separated  elements  that  were  set  free  by  the 
two  poles.  He  gave  the  names  which  are  still  used, 
and  the  process  he  called  electrolysis.  The  liquid 
decomposed  he  named  the  electrolyte ;  the  wire  by 
which  it  was  thought  the  current  entered,  he  called 
the  anode;  the  other,  the  cathode.  Those  particles 
which  moved  about  and  took  new  places  he  called 


236     CHEMICAL   ACTION    AND    ENERGY 

ions,  and  these  he  distinguished  as  anions  if  they 
went  to  the  anode,  and  cations  if  they  went  to  the 
cathode.  The  two  poles  together  have  since  been 
named  electrodes,  and  this  name  is  applied  to  them, 
whatever  their  shape  or  material. 

It  is  now  believed  that  each  of  the  ions  is  a  por- 
tion of  matter  carrying  electricity.  Because  the 
cation  moves  with  the  positive  electric  current,  and 
the  anion  against  it,  the  anions  are  considered  neg- 
ative, the  cations  positive. 

In  general,  the  metals  are  cations,  the  non-metals 
anions;  hence  metals  are  deposited  at  the  cathode, 
non-metals  and  their  compounds  at  the  anode.  Hy- 
drogen, however,  although  considered  a  non-metal, 
is  like  the  metals  in  being  electro-positive  and  ap- 
pearing at  the  cathode. 

While  some  electrolytical  actions  are  very  simple, 
others  are  exceedingly  complicated  and  difficult  to 
understand,  since  when  the  compounds  or  solutions 
are  separated  into  their  elements,  various  chemical 
actions  take  place,  producing  new  compounds. 
Even  the  separation  of  water  into  its  two  gases  is  be- 
lieved to  involve  a  series  of  changes  depending  on 
the  fact  that  in  order  to  conduct  electricity  the 
water  contains  sulphuric  acid,  which  is  decomposed 


il  from  '•  Younj's  Klvmentary  Principletof  Chemistry,"  by  per  mi  union  of  /).  Appleton  .f-  Company. 

SIR  HUMPHRY   DAVY 
B.  England,  1778.     D.  1829. 


CHEMICAL   ACTION    AND    ENERGY     237 

during  the  electrolysis.  It  is  formed  again,  how- 
ever, and  thus  does  not  change  in  amount,  serving 
merely  to  aid  the  changes  that  bring  about  the  re- 
lease of  hydrogen  and  oxygen. 

By  his  careful  measurement  of  the  amounts  of 
elements  liberated  at  the  different  poles,  Faraday 
established  a  law  which  has  become  of  enormous 
importance  in  the  study  of  chemistry.  He  proved 
"  when  the  same  quantity  of  electricity  acts  on  dif- 
ferent electrolytes,  the  ratio  between  the  quantities 
of  liberated  products  is  the  same  as  between  other 
chemical  equivalents."  To  put  the  same  idea  in 
simpler  language,  we  may  think  of  it  in  this  way: 
Separating  the  elements  by  electricity  gives  us  the 
same  amounts  that  are  found  when  they  are  sepa- 
rated by  other  agents.  In  other  words,  it  seems 
that  the  electricity  acts  upon  the  compound  only 
to  take  it  apart,  giving  us  the  same  results  as  if  we 
were  to  take  apart  the  elements  by  other  means. 

He  also  proved  that  the  same  result  followed 
always  for  the  same  amount  of  electricity,  whether 
it  were  used  strong  or  weak,  or  for  a  longer  or 
shorter  time.  This  enables  us  to  measure  precisely 
the  work  of  the  electric  current;  or  by  means  of 
the  work  we  may  measure  the  current. 


238      CHEMICAL  ACTION  AND  ENERGY 

Exactly  what  takes  place  in  electrolysis  is  not 
yet  certainly  known.  It  is  believed,  however,  that 
solutions  hold  the  elements  in  an  already  separated 
condition,  that  is,  the  solution  contains  free  atoms 
or  free  ions,  and  these  carry  the  electric  current 
from  one  pole  to  the  other.  When  electrically 
charged,  the  ions  and  atoms  move,  carrying  their 
charges  with  them  to  the  poles  that  attract  them 
according  to  whether  their  charge  is  positive  or 
negative.  Arriving  at  the  anode  or  cathode,  it  is 
believed  they  give  up  their  charges,  and  then  act 
or  re-act  chemically  on  one  another. 

SOLUTIONS 

For  a  long  time  in  the  past  it  was  the  commonly 
received  belief  that  when  solids  were  dissolved  in 
liquids,  the  solid  was  not  changed,  but  simply  be- 
came diffused  evenly  throughout  the  liquid,  though 
it  was  early  recognized  that  some  substances  when 
so  dissolved  combined  chemically  to  a  certain  ex- 
tent with  water.  When  experiments  in  electrolysis 
became  common,  it  was  discovered  that  solutions 
differed  very  greatly  in  the  property  of  conducting 
electricity.  Water,  when  pure,  was  so  poor  a  con- 
ductor that  it  might  be  said  not  to  carry  electricity 


CHEMICAL  ACTION   AND   ENERGY      239 

at  all.  When  an  acid,  base,  or  salt,  was  dissolved 
in  water,  the  solution  became,  usually,  an  excellent 
conductor  of  electricity,  though  the  power  of  con- 
ducting varied  widely.  Certain  compounds,  though 
they  enabled  electricity  to  be  conducted,  yet  could 
not  make  solutions  that  were  good  conductors. 

In  order  to  explain  the  differences  in  the  con- 
ducting power,  it  was  believed  that  when  solutions 
proved  to  be  good  conductors  it  was  because  the 
substances  dissolved  in  them  were  separated  into 
their  component  ions.  It  was  found,  too,  that  the 
conducting  power  of  solutions  depended  largely 
upon  whether  the  solution  was  richly  supplied  with 
the  substance  dissolved,  or  whether  the  solution 
was  very  diluted.  Other  points  also  were  noted  in 
experimenting  on  solutions.  The  most  important 
one  is  the  effect  of  dissolving  substances  in  water 
upon  the  boiling  and  the  freezing  points  of  the 
resulting  liquids.  When  compared  with  the  boil- 
ing or  freezing  points  of  water,  it  was  found  that 
the  solution  required  more  heat  to  raise  it  to  the 
boiling  point,  and  that  its  freezing  point  was  low- 
ered. And  this  raising  of  the  boiling  point  and 
lowering  of  the  freezing  point  is  exactly  propor- 
tioned to  the  molecular  weight  of  substances  dis- 


240      CHEMICAL  ACTION  AND  ENERGY 

solved.  To  illustrate  this — if  sugar  and  urea  are 
each  dissolved  in  water  in  the  same  proportion,  it 
is  found  that  the  raising  and  lowering  of  the  boil- 
ing point  and  freezing  point  bear  the  same  rela- 
tion to  one  another  in  the  two  solutions  that  the 
molecular  weight  of  sugar  bears  to  that  of  urea. 

It  will  be  seen  that  this  proportion  gives  chem- 
ists the  means  of  finding  the  molecular  weight  of 
a  substance.  We  may  take  a  substance  whose 
weight  is  known,  and  then  by  experimenting  deter- 
mine the  freezing  points  of  the  known  and  unknown 
substances.  We  may  then  make  a  proportion  saying 
that  as  the  molecular  weight  of  the  known  sub- 
stance is  to  that  of  the  unknown  substance,  so  is 
the  number  of  degrees  of  depression  of  the  freezing 
point  of  the  known  substance  to  the  number  of  de- 
grees of  the  depression  of  the  unknown  substance. 
This  law  has  been  found  to  give  results  that  agree 
closely  with  the  molecular  weight  found  by  other 
methods. 

But  when  acids,  bases,  or  salts  are  dissolved, 
making  solutions  that  convey  electricity,  the  law 
does  not  seem  to  apply  with  exactness,  and  the 
difference  in  results  seems  to  indicate  that  the  solu- 
tions which  conduct  electricity  are  not  the  same  as 


CHEMICAL  ACTION   AND    ENERGY      241 

the  solutions  which  will  not  conduct  it.  The  con- 
ducting solutions,  therefore,  are  believed  to  consist 
of  more  than  the  mere  results  of  dissolving  the 
substances.  They  not  only  dissolve,  but  dissociate 
substances,  separating  them  into  ions  to  some  ex- 
tent, as  well  as  into  their  molecules.  As  this  is  a 
difficult  thing  to  follow,  we  will  put  it  in  another 
way.  All  solutions  that  do  not  conduct  electricity 
come  under  the  law  by  which  their  boiling  and 
freezing  points  depend  upon  the  molecular  weight 
of  the  substances  dissolved.  If  the  electrolytes, 
when  acids,  bases,  and  salts  are  dissolved,  do  not 
agree  with  this  law,  it  is  because  they  are  different 
from  ordinary  solutions.  And  this  difference  is 
believed  to  consist  in  these  electrolytes  being  more 
than  mere  solutions;  that  is,  there  is  a  separating 
into  ions  as  well  as  into  molecules. 

In  NewelPs  "  Descriptive  Chemistry "  certain 
proofs  of  this  difference  are  given.  For  example, 
it  is  there  said  that  all  chlorides  when  in  solution 
respond  to  the  same  tests  chemically.  If  these  dif- 
fering compounds  retain  their  different  character, 
they  would  act  upon  tests  differently.  The  fact  that 
their  action,  despite  the  difference  in  their  composi- 
tion, is  the  same  on  all  tests,  seems  to  show  that 


242      CHEMICAL  ACTION  AND  ENERGY 

when  in  solution  the  chlorides  have  been  separated 
so  that  the  ions  of  chlorine  act  upon  the  test  rather 
than  the  molecules  of  the  chloride  compounds. 

Another  proof  of  the  same  thing  also  given  in 
NewelPs  book  is  the  fact  that  this  explanation  helps 

to  understand  the  action  of  all  acids,  bases,  and 

» 

salts,  when  in  solution.  The  actions  of  the  various 
solutions  are  such  as  they  would  be  if  the  com- 
pounds had  been  divided  in  the  solution  in  the  way 
this  theory  demands. 

A  third  proof  is  the  easy  explanation  of  neutral- 
ization given  by  this  ionic  theory.  When  an  acid 
solution  and  a  base  solution  are  mixed,  it  is  believed 
that  the  hydrogen  and  hydroxyl  (HO)  unite  to 
form  molecules  of  water.  When  hydrogen  and  the 
hydroxyl  ions  are  thus  allowed  to  combine,  the 
original  acid  and  the  original  base  having  lost  re- 
spectively the  hydrogen  and  the  hydroxyl  which 
gave  them  acid  and  basic  qualities  can  no  longer 
act  as  acid  or  as  base,  but  are  neutral. 

This  theory  of  solutions  is  comparatively  recent, 
but  it  is  very  helpful  in  explaining  many  chemical 
actions,  and  there  is  much  evidence  to  support  it 
in  the  deeper  facts  of  chemistry.  So  far  as  the 
young  reader  is  concerned,  he  need  remember  no 


CHEMICAL  ACTION   AND    ENERGY      243 

more  than  that  when  in  solution  chemical  com- 
pounds are  believed  to  be  in  such  a  state  that  they 
consist  of  particles  even  smaller  than  atoms,  and 
that  these  are  able  to  come  together  in  new  com- 
binations. In  order  to  know  what  these  combina- 
tions will  be,  it  is  necessary  for  the  chemist  to  know 
whether  the  ions  set  free  in  each  particular  com- 
pound entering  into  the  solution  are  positive  or  neg- 
ative, that  is,  whether  they  tend  to  go  to  the  posi- 
tive or  the  negative  pole  of  wires  conducting  elec- 
tricity through  a  solution.  For  it  is  believed  that 
the  positive  and  negative  ions,  like  the  differing 
poles  of  a  magnet,  attract  one  another,  and  that  the 
ions  of  the  same  polarity  repel  one  another,  or  go 
to  opposite  poles. 


CHAPTER   XV 
CHEMICAL  LAW.    THE  PERIODIC  SYSTEM 

HAVING  now  made  a  general  acquaintance  with 
the  commoner  elements  and  their  usual  compounds, 
we  are  ready  to  look  a  little  more  deeply  into  the 
Science  of  Chemistry,  and  to  become  somewhat 
familiar  with  its  important  laws. 

In  speaking  of  Dalton  in  an  earlier  chapter  we 
told  of  his  theory  of  molecules  and  atoms,  which  led 
to  the  law  of  definite  proportions — elements  com- 
bine always  in  fixed  proportions — and  the  law  of 
multiple  proportions,  that  these  proportions  if  they 
vary  in  forming  more  than  one  compound  of  the 
same  elements,  are  varied  in  simple  proportions. 

These  laws  lead  to  the  finding  of  numbers  show- 
ing the  combining  proportions  for  each  element. 
And  from  these,  by  taking  the  element  oxygen  at 
16  (or  hydrogen  at  1)  we  find  the  atomic  weights 
for  all  the  rest.  Thus  for  all  compounds  of  any 
element  we  have  a  number  which  shows  that  ele- 
ment's "  combining  weight " ;  and  in  its  compounds 

£45 


246  THE    PEKIODIC    SYSTEM 

we  find  either  just  that  weight,  or  even  repetitions 
of  it.  For  example,  we  find  in  oxides  either  16 
parts  of  oxygen  by  weight— or  16  X  2, 16  X  3,  and 
so  on. 

It  is  as  if  each  element  was  in  fixed  lumps,  not 
to  be  divided.  A  whole  lump  must  always  be  added 
or  taken  away  in  forming  compounds.  And  these 
imagined  "  lumps  "  are  atoms. 

Consequently  a  compound  must  be  made  up  of  a 
certain  whole  number  of  atoms  of  one  element,  and 
also  a  certain  whole  number  of  atoms  of  the  other. 
Therefore  the  weights  of  the  elements  in  the  com- 
pound must  compare  just  as  the  weights  of  two 
groups  of  atoms  compare.  Thus  HC1  is  hydro- 
chloric acid.  It  has  an  atom  of  hydrogen,  and  an 
atom  of  chlorine.  But  the  weight  of  the  hydrogen 
atom  is  1.008  and  of  the  chlorine  atom  is  35.45. 
So  by  a  simple  rule-of-three  operation  we  have  the 
proportion :  As  1.008  is  to  35.45,  so  is  the  weight  of 
the  hydrogen  to  the  weight  of  the  chlorine,  in  any 
amount  of  hydrochloric  acid.  Knowing  the  weight 
of  hydrochloric  acid,  we  can  find  both  weights. 

This  is  not  a  lesson  book,  so  we  won't  do  more 
than  show  the  rule.  H2SO4  is  sulphuric  acid,  and 
this  contains  two  atoms  of  hydrogen,  one  of  sul- 


THE    PERIODIC    SYSTEM  247 

phur,  and  four  of  oxygen.  Consequently  its  parts 
by  weight  are: 

H 2  X    1.008=  2.016 

S 1X32.06    —32.06 

O 4  X  16         =64. 

98.076 

So,  dropping  the  fractions,  there  are  %s  of  H,  3%s 
of  S,  and  6%s  of  O — from  which  you  can  readily 
put  the  numbers  into  percentages  or  any  sort  of 
measures. 

From  this  also  you  see  that  each  molecule  of  the 
sulphuric  acid  (containing  all  three)  is  nearly  a 
hundred  times  the  weight  of  an  atom  of  hydro- 
gen. Water,  being  H2O,  its  molecule  weighs 
2.016  +  16  =  18.016,  and  is  therefore  about  %  as 
heavy  as  the  molecule  of  sulphuric  acid. 

Now,  since  we  cannot  separate  molecules  and 
count  them,  or  get  equal  groups  together,  this  com- 
parison seems  useless. 

But  remember  that  matter  has  several  states — 
solid,  liquid,  and  gaseous.  And  when  we  study 
gases  we  shall  find  more  help  in  this  comparison 
of  molecules. 


248  THE    PERIODIC    SYSTEM 

Gases  are  believed  to  consist  of  molecules  sepa- 
rated and  in  constant  motion — for  they  may  be  com- 
pressed ;  gases  when  unconfined  tend  to  become  less 
dense;  and  they  will  mix  freely  one  with  another. 
Their  molecules,  too,  are  found  alike  in  all  por- 
tions. Now  in  1660  the  English  philosopher  Boyle 
showed  that  it  was  almost  exactly  true  that  a  gas 
always  fills  the  same  space  under  the  same  heat 
and  pressure,  and  that  gases,  at  the  same  tempera- 
ture, resist  pressures  alike.  Also,  heating  and 
cooling  affect  gases  alike  in  changing  volume  and 
pressure,  as  was  shown  later  by  Dalton  and  others. 

The  pressure  of  gases  is  believed  to  come  from 
the  striking  of  the  moving  molecules  against  the 
vessel  that  confines  them.  Study  of  the  laws  that 
govern  the  increasing  pressure  has  led  to  the  belief 
that  the  loss  of  volume  in  compressing  gases  comes 
from  crowding  the  molecules  nearer  together,  and 
that  the  molecules  seem  to  move  in  straight  lines — 
though  they  do  not  repel  one  another.  Heat  is  be- 
lieved to  increase  the  velocity  of  the  molecules' 
motion. 

From  these  facts  and  theories  an  Italian  profes- 
sor, Amadeo  Avogadro,  in  1811  suggested  that  "  all 
gases  at  the  same  pressure,  temperature,  and  vol- 


THE    PERIODIC    SYSTEM  249 

ume  contain  the  same  number  of  molecules."  This 
has  been  generally  accepted,  and  under  the  name 
Avogadro's  Law  has  been  applied  to  reasoning  out 
the  weights  of  molecules  and  atoms,  and  the  ex- 
plaining of  other  chemical  facts. 

Now  this  law  means  that  at  the  same  temperature 
and  pressure — as  in  a  closed  box,  kept  at  a  certain 
heat,  and  with  a  gauge  that  would  show  when  a 
gas  within  was  at  the  same  tension — the  number  of 
molecules  is  the  same,  and  that  they  are  at  the  same 
distance  apart.  It  has  proved  a  generally  true 
law,  with  only  the  very  smallest  exceptions — and 
these  are  thought  to  be  explained  or  at  least  under- 
standable. 

If  now  we  find  that  equal  volumes  of  gases  under 
equal  heat  and  pressure  differ  in  weight,  we  argue 
that  the  molecules  differ  in  weight  in  that  propor- 
tion. And  thus  we  can  get  at  the  relative  weight 
of  the  molecules;  for  if  the  same  volume  (at  same 
heat  and  pressure)  is  double  the  weight  of  another 
gas,  we  say  this  is  because  the  first  has  the  same 
number  of  molecules,  each  of  twice  the  weight  of 
the  molecules  of  the  second  gas. 

Only  the  larger  books  on  chemistry  can  af- 
ford space  to  explain  fully  the  applying  of  this 


THE    PEKIODIC    SYSTEM 

law,  and  the  correcting  of  the  slight  differences 
found  between  the  facts  found  in  the  laboratory 
and  those  the  theory  requires.  We  intend  only  to 
show  the  method  of  reasoning  used. 

Now,  in  the  case  of  water,  experiment  shows 
that  two  volumes  of  hydrogen  unite  with  one  of 
oxygen  and  form  water,  making  two  volumes.  Sup- 
posing we  are  dealing  with  100  molecules  in  each 
volume.  Then  100  H-molecules  +  100  H-molecules 
Join  100  O-molecules,  and  give  us  200  water  mole- 
cules. But  each  of  these  must  contain  an  equal 
part  of  oxygen  molecules.  So  the  100  O-molecules 
have  been  divided  into  200  parts.  Therefore  each 
water-molecule  contains  H  (1  molecule  or  2  atoms) 
and  O  (1  atom).  So  the  expression  of  the  atoms 
in  a  water  molecule  becomes  H2O. 

But  this  indicates  that  each  molecule  of  oxygen  is 
made  up  of  two  atoms — which  may  be  single  parti- 
cles or  groups  of  electrons. 

Though  this  reasoning  is  based  on  the  idea  of 
atoms  and  molecules,  yet  the  relations  of  the  ele- 
ments thereby  found  are  true,  and  would  remain 
even  if  that  idea  were  given  up,  as  is  well  set  forth 
in  A.  Smith's  "  General  Inorganic  Chemistry." 

When  we  have  reduced  various  compounds  to 


THE    PERIODIC    SYSTEM  251 

gases  at  the  same  pressure  and  temperature,  we  can 
then  find  out  their  molecular  weight.  Analysis 
shows  their  composition,  and  knowing  the  propor- 
tion of  each  element  in  the  compound,  we  can  find 
its  molecular  weight,  and  its  atomic  weight — and 
all  these  may  then  be  put  into  tables  on  the  same 
scale. 

The  molecular  weight  of  any  element  or  com- 
pound means  the  weight  of  its  molecule  compared 
with  that  of  oxygen  or  hydrogen.  It  is  found  by 
adding  together  all  the  atoms  in  a  compound,  each 
multiplied  by  its  atomic  weight. 

It  is  by  this  method  (as  well  as  others)  that  the 
weights  given  the  elements  in  the  accepted  tables 
have  been  found  or  verified. 

Another  law,  known  as  that  of  Dulong  and  Petit, 
declares  that  the  atomic  weight  of  any  element 
when  multiplied  by  itg  specific  heat  in  the  solid 
state  produces  the  same  number  as  comes  from  the 
same  factors  of  any  other  element.  This  means 
that  equal  numbers  of  atoms  require  the  same  heat 
to  raise  their  temperature  the  same  amount.  The 
atomic  weight  has  been  defined.  The  specific  heat 
is  the  amount  of  heat  necessary  to  raise  the  temper- 
ature of  any  element  one  degree,  compared  with 


252  THE    PEKIODIC    SYSTEM 

the  amount  of  heat  necessary  to  raise  water  one 
degree. 

This  law  may  be  put  in  another  way,  thus:  If 
the  atomic  weight  of  any  element  be  multiplied  by 
its  specific  heat,  the  result  will  be  a  fixed  number. 
This  number  varies  between  6  and  7  for  most  ele- 
ments, and  this  rule  helps  to  verify  atomic  weights 
found  in  other  ways.  To  give  a  few  examples: 

At.  wt.     Sp.  heat 

Lithium 7.03  X  .94     ==  6.60 

Uranium   238.5    X  .0276  =  6.582 

Calcium 40.1    X  .17      =  6.81 

Gold 197.2    X  .032   =  6.31 

If  the  comparison  had  been  made  with  another 
standard  than  water  (for  the  unit  of  specific  heat) 
the  figure  6.  -f-  would  be  different.  But  the  impor- 
tant matter  is  the  fact  that  the  relation  between 
specific  heat  and  atomic  weight  is  a  fixed  one  with 
elements  when  in  solid  state. 

In  A.  Smith's  Chemistry  this  law  is  explained 
thus :  In  equal  weights  of  elements,  there  are  fewer 
chemical  units  as  the  weight  of  these  is  greater, 
and  so  few  chemical  units  require  less  heat  to  raise 
them  equally  in  temperature. 


THE    PERIODIC    SYSTEM  253 

All  these  views  of  substances,  and  these  laws  ex- 
plaining the  making  of  compounds,  the  actions  of 
gases,  the  forming  of  a  certain  volume  of  gas,  and 
so  on,  come  from  the  general  idea  that  matter  con- 
sists of  elements,  elements  of  molecules,  and  these 
of  atoms.  Whether  this  be  true  or  not,  it  has 
helped  us  to  understand  results. 

Now  we  know  that  elements  combine  in  certain 
weights  or  "  equivalents."  We  believe  these  are 
formed  by  atoms  or  groups  of  atoms.  Believing  in 
atoms,  we  can  see  reasons  for  the  changes  in  the 
volumes  of  gases,  for  the  law  of  specific  heat,  and 
for  the  differences  in  various  molecules.  It  is  only 
when  we  come  to  study  electrolysis  and  solutions 
that  we  need  to  consider  the  breaking  up  of  atoms 
into  smaller  portions — as  has  already  been  sug- 
gested. 

Accepting,  then,  the  belief  in  atoms,  and  their 
weights,  we  may  examine  into  the  relations  of  the 
elements  as  each  made  up  of  like  atoms,  differing 
in  weight  and  material  from  other  atoms.  If  we 
put  the  elements  in  regular  order  according  to  their 
atomic  weights,  we  shall  find  that  there  seems  to 
be  a  certain  relation  between  elements  that  fall 
into  similar  places  in  the  table.  The  law  shown 


254  THE    PEEIODIC    SYSTEM 

by  a  table  of  elements  so  arranged  is  known  as  the 
Periodic  Law. 

This  arranging  of  elements  was  first  suggested  in 
1863  by  Newlands,  but  has  been  improved  by  others, 
notably  by  Meyer  and  Mendeleef.  The  table  of 
elements  used  to-day  is  known  as  Mendeleefs 
table,  and  is  shown  on  page  255. 

Many  other  forms  may  be  used  in  presenting  this 
table,  but  the  general  idea  is  to  arrange  the  ele- 
ments so  as  to  show  that  there  exist  certain  groups 
which  when  brought  together  without  changing  the 
general  order  (according  to  atomic  weights)  will 
make  it  plain  that  there  are  many  relations  between 
the  elements. 

Along  the  top  of  the  table  are  Roman  numbers. 
These  show  what  is  known  as  the  valency  of  the 
elements.  Valency  is  defined  as  the  property  that 
elements  possess,  when  entering  into  compounds,  of 
replacing  one  another.  Thus  all  elements  that  have 
the  valency  (or  valence)  "one"  may  combine 
with  or  replace  others  of  the  same  valency,  atom 
for  atom.  Those  that  have  a  valency  of  "  two  " 
can  combine  with  or  replace  each  other  atom  for 
atom,  or  can  replace  two  atoms  of  the  elements  of 
valency  "  one,"  and  so  on.  Thus  oxygen  has  the 


THE    PERIODIC    SYSTEM 


OJ^ 
HH> 


fa 


CO 

Oco 


I 


1-1  00 


Sff 

Ocfl 


05  < 


_  be 

OS 


05  ,£5 


Oi   C3 

^^ 
S]    ' 


r— i  ,*-. 

^S 


52 
i— i  ^- 

S 


,3 


X 


i3 


255 


256  THE    PEEIODIC    SYSTEM 

valence  II,  and  combines  with  two  atoms  of  hydro- 
gen for  each  atom  of  its  own.  Carbon  has  the 
valency  IV  (or  II),  and  thus  combines  with  other 
elements  accordingly.  Many  elements  have  more 
than  one  valency,  as  the  table  shows. 

Elements  are  named  thus,  according  to  valency, 
from  the  Greek  numbers: 

I,  Monad;  II,  Dyad;  III,  Triad;  IV,  Tetrad; 
V,  Pentad;  VI,  Hexad;  VII,  Heptad;  VIII,  Octad. 
The  adjectives  are,  monovalent,  divalent,  and  so  on 
to  the  end. 

In  its  first  column  the  valence  O  appears.  This 
means  that  the  elements  in  that  column — Helium, 
Neon,  Argon,  Krypton,  Xenon,  rare  gases  in  the 
air  and  elsewhere — show  no  compounds. 

We  may  know  the  valence  of  any  element  in  a 
compound  by  seeing  how  many  of  its  atoms  are 
found  combined  with  those  whose  valence  is  known. 
Thus,  in  OsO4  (osmic  acid),  since  O  has  the  valence 
II,  and  there  are  4  O-atoms  to  1  of  osmium,  we  see 
that  osmium  must  have  the  valence  VIII,  as  the 
table  gives  it. 

The  table  shows  how  valence  changes  with  atomic 
weight — rises  and  falls,  periodically.  Thus,  take 
the  horizontal  row  beginning  with  Ne  (neon)  at 


THE    PERIODIC    SYSTEM  257 

O  valence,  we  have  Na  (sodium)  I,  Mg  (magne- 
sium) II,  aluminium  III,  silicon  IV,  phosphorus  V 
(sometimes)  or  lower,  sulphur  VI  (or  lower), 
chlorine  VII  (or  at  times  I).  It  is  as  if  valence 
grew  with  weight,  till  it  passed  a  certain  point, 
and  then  increased  or  diminished  according  to  the 
circumstances.  This  difference  in  valence  corre- 
sponds with  the  different  "  equivalents  "  by  which 
elements  form  compounds.  Thus  formula  NH4C1 
(ammonium  chloride)  shows  nitrogen  as  a  pentad, 
combining  with  an  atom  of  monad  chlorine  and 
four  atoms  of  monad  hydrogen.  Other  formulas 
may  be  read  in  the  same  way. 

This  relation  in  valency  is  only  one  of  the  resem- 
blances brought  out  by  this  "  Periodic  System." 
In  general,  the  properties  of  the  elements  increase 
or  decrease  with  the  atomic  weights.  To  perceive 
this  a  wide  knowledge  of  chemistry  would  be  neces- 
sary, but  we  may  rest  satisfied  with  the  general 
notion  that  the  table  brings  together  the  elements 
in  like  groups,  and  that  the  groups  change  regu- 
larly as  we  move  up  and  down  the  columns,  or 
across  the  rows,  to  and  fro. 

Thus  in  the  first  column  we  find  rare,  inactive 
elements.  In  the  second,  beginning  with  lithium, 


258  THE    PERIODIC    SYSTEM 

the  lightest  metal,  we  get  heavier  metals,  with 
stronger  metallic  qualities,  until  we  reach  copper, 
silver,  and  gold.  The  third  column  also  is  increas- 
ingly metallic  till  we  reach  mercury,  and  below  it 
(probably)  comes  radium — which  can  be  rightly 
put  with  mercury,  the  liquid  metal,  for  it  seems 
almost  a  gas-metal.  Column  fourth  begins  with 
carbon  and  silicon — the  two  great  foundations  of 
organic  and  inorganic  compounds — and  also  leads 
to  dense  metals — lead  and  thorium. 

Horizontally,  from  lithium,  lightest  metal,  we 
proceed  to  the  gas  fluorine;  from  sodium  to  chlo- 
rine; from  potassium  to  manganese — in  each  case 
progressing  regularly  in  power  to  combine  with  oxy- 
gen, or  valence  toward  that  element.  In  each  row, 
the  last  four  regularly  lose  valence  toward  hydro- 
gen (if  they  combine  at  all).  Specific  gravities" 
also  will  be  found  to  be  according  to  certain  orders 
in  the  table. 

But — for  its  many  striking  features,  chemical 
treatises  must  be  consulted.  We  will  only  pause 
to  say  that  since  the  table  was  first  made,  it  has  led 
to  the  discovery  of  at  least  three  new  elements  to 
fill  spaces  that  were  blanks  (scandium,  1879,  gal- 
lium in  1875,  and  germanium,  1888).  These  Men- 


THE    PERIODIC    SYSTEM  259 

dele"ef  predicted — with  others  not  yet  found.  The 
table  also  helps  to  fix  doubtful  atomic  weights,  and 
suggests  lines  of  work  to  chemists,  while  it  helps 
to  classify  the  elements,  and  to  confirm  discoveries 
and  researches. 


CHAPTER   XVI 

THE  STORY  OF  CHEMISTRY 

IN  very  truth  the  story  of  chemistry  might  begin 
with  man's  use  of  fire,  or  with  the  earliest  use  of 
metals,  and  we  have  already  seen  that  speculation 
about  what  substances  were  made  of  began  far  back 
even  of  the  alchemists.  But  in  a  true  sense,  if  we 
wish  to  know  about  the  modern  science  of  chemis- 
try we  can  hardly  go  further  back  than  the  English 
philosopher,  Eobert  Boyle. 

Before  his  century,  even,  hundreds  of  compounds 
were  made  in  the  East  and  in  Europe,  and  there  are 
names  of  great  experimenters  such  as  Albertus 
Magnus,  Roger  Bacon,  Raymond  Lulli,  and  Para- 
celsus, who  were  wise  for  their  time,  and  held  views 
more  or  less  correct  about  chemical  questions.  But 
with  Robert  Boyle  we  first  have  the  idea  of  widely 
applicable^laws  and  theories,  as  against  the  fanci- 
ful superstitions  of  the  alchemists.  Boyle  was 
against  all  such  wild  notions,  and  wrote  a  book 
pointing  out  the  absurd  claims  and  ridiculously 
stilted  language  of  the  chemists  of  his  time. 

261 


262        THE   STOKY   OF    CHEMISTRY 

Boyle  belonged  to  a  society  known  as  the  "  Invisi- 
ble College,"  a  body  of  men  interested  in  science 
and  the  arts,  that  afterward  gave  rise  to  the  Royal 
Society.  Boyle  championed  the  view  that  all  mat- 
ter was  made  up  of  smaller  particles  or  bodies,  and 
urged  the  need  of  making  true  experiments,  and  of 
setting  forth  results  in  plain  language  all  men 
might  understand.  With  him  true  analysis  of  sub- 
stances began.  To  him  we  owe  that  great  princi- 
ple, "  Boyle's  Law,"  discovered  by  him  in  1660 — at 
an  unchanged  temperature  any  gas  occupies  less 
volume  as  the  pressure  is  greater — that  is,  double 
the  pressure  and  the  volume  is  halved ;  or  halve  the 
pressure  and  the  volume  is  doubled.  This  has 
become  the  very  foundation  stone  of  modern 
ideas  about  how  matter  is  made  up,  for  on  it  is 
based  the  theory  of  atoms,  and  all  that  has  fol- 
lowed. 

Next  to  Boyle  should  be  mentioned  Priestley,  con- 
cerning whom  it  is  interesting  to  know  that  it  was 
Benjamin  Franklin's  gift  of  some  books  on  elec- 
tricity that  formed  the  turning  point  in  Priestley's 
life,  leading  him  toward  science.  Though  Priestley 
believed  some  of  the  mistaken  notions  of  his  day,  yet 
to  him,  with  the  great  Lavoisier,  is  due  the  honor  of 


THE   STORY    OF    CHEMISTRY        263 

discovering  the  composition  of  air  and  the  element 
oxygen.  Priestley,  by  means  of  a  burning-glass 
lens  heated  "the  calx  of  mercury"  (mercury 
oxide)  and  found  that  "air"  was  given  off  under 
a  bell-glass.  This  "air  "  when  tested  was  seen  to 
be  something  unknown,  and  its  study  was  the  dis- 
covery of  oxygen.  Priestley  also  invented  the 
"  pneumatic  trough  "  for  collecting  gases.  He  sep- 
arated ammonia  into  its  gases — hydrogen  and  ni- 
trogen, and  made  studies  upon  the  nature  of  com- 
bustion— which  in  his  day  was  believed  to  consist 
in  the  driving  out  of  an  imagined  substance  called 
"phlogiston."  Priestley  himself  shared  this  the- 
ory. When  it  was  shown  that  a  burned  substance 
sometimes  gained  in  weight  (by  absorbing  oxygen, 
of  course),  the  believers  in  phlogiston  were  forced 
to  argue  that  it  might  be  a  substance  of  "  negative 
gravity."  Oxygen  was  first  called  "  dephlogisti- 
cated  air  "  and  nitrogen  "  phlogisticated  air  "  from 
this  theory. 

The  next  English  chemists  of  note  were  Black,  an 
opponent  of  phlogiston,  who  discovered  "  carbonic 
acid  gas  "  (CO2)  and  proved  its  relations  to  certain 
carbonates  of  alkalies  and  alkaline  earths;  and 
Henry  Cavendish,  the  strange,  interesting  recluse 


264        THE   STOEY    OF    CHEMISTRY 

who  showed  the  composition  of  air,  that  of  water, 
and  who  studied  deeply  into  the  nature  of  heat.  To 
him  is  due  the  discovery  of  hydrogen  and  its  unit- 
ing with  oxygen  to  form  water  when  burned;  and 
much  study  of  the  weight  of  gases.  He  showed 
how  the  calcium  carbonate  was  dissolved  by  water 
containing  carbon  dioxide,  and  analyzed  nitric 
oxide.  Many  amusing  anecdotes  are  told  of  his 
eccentricities  and  his  shyness. 

Then  the  great  names  become  frequent,  for  the 
true  path  to  chemical  knowledge  was  becoming 
known.  Of  Dalton  we  have  told  already,  and  we 
will  only  remind  the  reader  of  his  atomic  theory 
and  of  the  law  of  multiple  proportions,  which 
certainly  were  first  clearly  put  forth  under  his 
name. 

The  law  of  definite  proportions  was  at  this  time 
much  disputed.  The  great  champions  were  Ber- 
thollet  and  Proust — the  former  urging  that  ele- 
ments combined  in  many  unfixed  amounts,  and  that 
solutions  in  all  degrees  might  be  regarded  as  com- 
pounds. It  was  early  in  the  nineteenth  century 
that  Proust's  party  succeeded  in  showing  that  mix- 
tures were  not  compounds,  and  Berthollet's  party 
were  compelled  to  admit  the  law.  During  this  con- 


Itcprodueed  from  "  Young'*  Elementary  Principles  of  Chemistry,"  Inj  permixRinn  of  D.  Appletoii  ,E-  Company 

JOSEPH   Louis    GAY-LUSSAC 
B.  France,  1778.     D.  Paris,  1850. 


THE   STORY   OF    CHEMISTRY        265 

troversy  much  information  was  acquired  by  the  dis- 
putants, and  Dr.  Wollaston,  famous  in  electric 
science,  pointed  out  that  elements  combined  in 
multiple  proportions — which  completed  the  rule, 
"  elements  combine  in  definite  and  multiple  propor- 
tions " — as  we  have  seen. 

The  same  period  saw  from  the  French  chemist, 
Gay-Lussac,  a  publication  pointing  out  the  laws 
of  the  combination  of  gases — that  these  combine  in 
definite  proportions  if  under  the  same  heat  and 
pressure,  and  form  fixed  volumes — which  led  to  the 
theory  announced  by  Avogadro  concerning  the  rea- 
son for  the  result.  The  idea  that  each  gas  con- 
tained compound  atoms  (molecules)  in  equal  num- 
ber proved  a  most  fruitful  one;  and  the  word 
"  molecule  "  took  its  place  in  the  science — but  only 
in  after  years  was  the  discovery  accepted,  together 
with  the  atomic  theory  in  completer  form. 

The  proving  of  the  theory  is  credited  to  Ber- 
zelius,  a  Swedish  chemist,  and  Thomson,  a  Scotch 
professor.  Berzelius  was  a  great  analyst,  and 
tested  the  theory  in  his  laboratory,  making  experi- 
ments to  confirm  the  combining  of  elements  in  fixed 
proportions.  To  him  is  due  the  system  of  letters 
and  numbers  that  enable  us  to  write  chemical  for- 


266        THE    STORY    OF    CHEMISTRY 

mulas.  This  way  of  writing  the  results  of  ex- 
periments made  the  theory  evident  and  widely 
known. 

Next  came  Dulong  and  Petit's  experiments,  show- 
ing that  the  elements  had  "specific  heat"  accord- 
ing to  their  atomic  weights,  and  the  discovery  by 
a  German  chemist  that  "  elements  having  the  same 
number  of  atoms  to  the  molecule  are  disposed  to 
form  the  same  angles  of  crystallization."  This  is 
known  as  "isomorphism,"  from  isos,  like,  and 
morphos,  form. 

Dr.  Henry  Smith  Williams  in  his  article,  "  The 
Century's  Progress  in  Chemistry  "  (Harper's  Maga- 
zine), sets  forth  these  facts  much  more  fully,  and 
shows  how  the  atomic  theory  gradually  became  an 
indisputable  part  of  chemistry  and  the  forerunner 
of  the  modern  science.  I  have  not  met  with  a  bet- 
ter brief  history  of  the  science  and  have  been  greatly 
aided  by  his  article  in  this  chapter. 

With  Sir  Humphry  Davy  the  union  of  the 
sciences  of  chemistry  and  electricity  began,  and 
almost  at  once  enabled  him  to  make  brilliant  dis- 
coveries. He  first  separated  potassium  and  sodium 
as  metals  from  their  compounds,  and  soon  in  the 
same  way  discovered  calcium,  barium,  and  stron- 


THE   STORY   OF    CHEMISTRY        267 

tium.  On  decomposing  water,  various  substances 
besides  hydrogen  and  oxygen  were  set  free  at  the 
poles,  but  Davy  was  able  to  prove  that  these  were 
impurities  derived  from  the  apparatus. 

Meanwhile  a  theory  had  grown  up  that  all  com- 
pounds were  built  up  of  "  binary  "  combinations  of 
"  positive  "  and  "  negative  "  atoms ;  and  this  was 
championed  by  Berzelius  with  much  ability.  It 
had  many  facts  in  its  favor,  such,  for  example,  as 
the  persistence  of  the  "  radicals,"  of  which  Gay- 
Lussac  in  1815  had  discovered  cyanogen  (CN)  and 
Ampere  had,  a  year  later,  discovered  ammonium 
(NH)  ;  and  for  years  it  was  widely  accepted. 

But  later  investigations,  and  increase  of  skill  in 
the  putting  together  of  compounds  were  to  show 
there  was  no  such  general  law.  Its  overthrow  came 
soon  after  Wbhler's  achievement  in  making  the  or- 
ganic compound,  urea.  This  opened  the  way  to 
the  conquest  of  organic  chemistry,  and  brought 
about  the  study  of  carbon  and  its  compounds  that 
led  Liebig  to  his  triumphs  in  agricultural  chemis- 
try— the  study  of  the  enrichment  of  soils  and  the 
improvement  of  food-stuffs;  and  also  saw  the  entry 
upon  the  same  field  of  the  French  chemists,  Dumas 
and  Pasteur. 


268        THE   STOEY   OF    CHEMISTRY 

The  studies  in  organic  chemistry  revealed  many 
radicals — and  many  of  them  were  binary  com- 
pounds. But  Dumas  was  able  to  substitute  oxy- 
gen, a  "  positive "  element,  for  the  "  negative  " 
element  chlorine,  and  thus  to  show  that  the  binary 
theory  of  Berzelius  was  not  a  law. 

This  led  to  further  investigation  and  speculation 
in  regard  to  the  make-up  of  molecules,  and  brought 
about  the  proof  that  certain  molecules  must  contain 
more  than  one  atom  of  the  same  element.  As  pre- 
viously shown,  if  hydrogen  unites  with  oxygen, 
making  one  volume  of  oxygen  -}-  two  volumes  of 
hydrogen  =  two  volumes  of  water-vapor,  then  the 
molecules  of  oxygen  must  have  split  into  two  atoms. 
If  so,  the  oxygen  molecule  is  O2. 

Similar  reasoning  with  other  elements  and  com- 
pounds brought  out  the  theory  of  "  valency,"  and 
of  the  exchange  of  atoms  in  the  forming  of  com- 
pounds. This  was  a  great  gain  for  several  reasons. 
It  explained  that  there  was  a  limit  to  the  com- 
binations of  certain  elements  with  one  another. 
Knowing  that  the  valencies  of  H,  O,  N,  and  C 
were  I,  II,  III,  IV,  respectively,  it  was  evident  that 
H  and  O,  for  example,  could  only  combine  thus, 
H— O— ,  H— O— H,  H— O — O — H,  and  that  all 


Ktn>mliif,i-,l  from  "  Youny's  Elementary  Principles  of  Chemistry,"  by  permission  of  I).  Appleton  &  Company. 

JOSEPH    BLACK 
B.  Bordeaux,  1728.     D.  Edinburgh,  1799. 


THE   STORY   OF    CHEMISTRY        269 

these  had  used  their  valencies  except  the  first  H — 
O — ,  which  was  less  stable  than  the  others,  or  could 
not  stand  alone.  It  also  showed  what  was  meant  by 
the  "  isomerism  "  discovered  by  Liebig  and  Wohler 
— the  existing  of  differing  compounds  that  yet  were 
made  up  of  the  same  number  and  the  same  kind  of 
atoms.  And  this  led  to  the  close  study  of  how 
atoms  were  grouped — as  shown  by  graphic  formulas 
— such  as  we  saw  in  the  chapter  on  carbon  com- 
pounds, and  also  of  their  action  in  entering  or 
leaving  these  groups.  Out  of  these  studies  have 
come  the  ideas  of  "  disassociation  " — the  tendency 
of  atoms  to  leave  one  combination  and  enter  an- 
other, and  the  "  reversibility  "  of  chemical  combi- 
nation— or  the  tendency  in  many  cases  of  a  chem- 
ical action  to  swing  back  again  to  its  first  condi- 
tion if  the  elements,  molecules,  or  atoms  are  not 
separated  or  set  free  in  some  way  at  some  stage  of 
their  movements. 

All  these  views  tend  to  increase  the  complexity 
of  chemical  study,  and  at  the  same  time  to  make 
actions  and  reactions  better  understood,  and  more 
capable  of  control.  The  subject  became  deeply 
specialized,  and  the  mass  of  facts  accumulated  was 
so  enormous  that  chemists  longed  for  some  simpli- 


270        THE   STORY   OF    CHEMISTRY 

fying — for  general  laws  that  would  make  the  knowl- 
edge systematic. 

The  earliest  steps  toward  this  desired  end  were 
in  an  attempt  to  show  that  there  were  not  so  many 
elements — that  possibly  some  of  them  were  com- 
pounds, and  that  study  might  prove  there  were 
but  few  real  "elements."  It  was  even  suggested 
by  Prout,  in  1815,  that,  since  many  of  the  atomic 
weights  were  multiples  of  the  atomic  weight  of 
hydrogen,  it  might  be  all  elements  were  but  forms 
or  compounds  of  this  single  one.  In  1840,  Dumas 
made  some  attempts  toward  a  possible  proof  of 
this  theory,  but  it  would  not  lend  itself  to  proof. 

Help  came  in  another  way.  In  1864  the  chemist, 
John  Newlands,  showed  that  if  the  elements  were 
put  in  the  order  of  their  atomic  weights,  there 
seemed  to  be  a  law  of  "  octaves,"  and  this  led  to  the 
studies  of  the  American,  Hinrichs,  the  German, 
Meyer,  and  the  Russian,  Mendeleef — with  the  re- 
sult already  explained  in  discussing  the  Periodic 
System. 

Another  help  was  found  in  the  spectroscope.  By 
the  aid  of  this  instrument,  and  of  photography,  it 
was  possible  to  examine  and  compare  the  spectra 
of  bodies,  not  only  on  earth,  but  in  the  heavens. 


THE   STORY   OP    CHEMISTRY        271 

Its  revelations  of  the  gradual  simplifying  of  ele- 
ments present,  as  hotter  and  hotter  stars  are  exam- 
ined— there  being  only  one-half  of  our  list  in  the 
sun,  and  still  fewer  in  Sirius — was  taken  as  an 
encouragement  to  the  belief  that  elements  here  un- 
changeable might  under  other  circumstances  be 
shown  to  be  compounds. 

We  cannot  discuss  every  important  step  made  in 
more  recent  years,  as  again  the  great  mass  of  mate- 
rial forbids.  But  since  the  discovery  of  the  Ront- 
gen  rays — the  x-rays,  in  1905,  there  has  been  a 
most  startling  advance  in  the  study  of  matter.  Fol- 
lowing Rontgen  came  the  French  chemist,  Bec- 
querel,  with  the  discovery  of  "  rays  "  from  uranium, 
and  the  German,  Schmidt,  who  found  rays  from 
thorium.  Then,  at  BecquereFs  instance,  M.  and 
Mme.  Curie  made  a  thorough  examination  of  the 
elements,  and  found  no  "  rays  "  except  in  these  two 
— uranium  and  thorium.  But  rays  were  abundant 
in  certain  minerals — especially  pitchblende,  where- 
from  came  rays  even  stronger  than  those  from  ura- 
nium. 

Patient,  heroic  work  began.  A  car-load  of 
pitchblende  was  laboriously  analyzed,  and  out  of 
it  was  secured  one-quarter  of  a  grain  of  chloride  of 


272        THE   STORY   OF    CHEMISTRY 

"  radium " — a  new  element.  This  was  the 
%ooooooth  part  of  the  pitchblende,  and  the  quarter 
grain  had  been  evenly  diffused  throughout!  Its 
cost  was  at  the  rate  of  $25,000,000  a  kilogram. 

Then  began  the  study  of  the  new  element,  and 
of  its  three  kinds  of  rays — known  as  a,  y? ,  and  7-  — 
alpha,  beta,  and  gamma  rays.  This  study  was  ex- 
haustive, accurate,  and  complete.  It  has  been  veri- 
fied by  observers  throughout  the  world,  and  leads 
to  most  amazing  conclusions.  When  certain  of  these 
rays  or  emanations  are  collected  in  a  glass  tube, 
and  subjected  to  examination,  it  has  been  found 
that  there  is  no  trace  of  radium,  but  that  in  the 
tube  is  a  gas — the  gas  of  the  element  helium,  as 
the  spectrum  of  it  proves. 

Again  we  must  condense.  Let  us  say  in  brief 
that  here  are  some  of  the  chemists'  conclusions: 
In  pitchblende,  where  uranium  is  found,  is  found 
also  a  proportionate  amount  of  radium.  From  the 
uranium,  it  is  believed,  may  come  the  radium. 
Then  the  "  rays  "  from  radium  change  into  helium. 
From  helium  there  is  a  further  change  to  polonium, 
another  new  element.  Thus  the  chain  already 
formed  seems  to  show  an  element  (uranium)  giv- 
ing rise  to  three  others, — and  it  is  thought  also 


Reproduced  from  "  Young's  Elementary  Principles  of  Chemistry,"  by  permission  of  D.  App'eton  ,t-  Company. 

CLAUDE   Louis    BERTIIOLLET 
B.  Savoy,  1748.     D.  Paris,  1822. 


THE   STORY   OF    CHEMISTRY        273 

that  when  the  uranium  shall  have  ceased  to  send 
forth  its  emanations,  that  which  is  left  of  it  will 
be  another  element — this  time  a  familiar  one — the 
heavy,  inert,  metallic  element,  lead. 

Such  is  the  most  recent  evidence  that  there  is 
hope  that  the  elements  may  be  simplified  in 
number. 

It  is  impossible  not  to  recall  the  gradual  steps  by 
which,  beginning  with  the  masses  of  matter  them- 
selves, men  have  come  to  believe  these  made  up  of 
molecules, — have  then  been  forced  to  seek  further 
for  the  atoms  that  compose  molecules ;  and  are  now 
finding  in  the  atoms — so  much  else. 

We  have  been  forced  to  see  electrons  in  the  radio- 
active bodies,  ions  and  kations  in  solutions,  and 
to-day  speculation  is  busy  in  trying  to  get  within 
the  orbits  of  electrons,  hoping  to  know  whether 
there  is  a  central  nucleus  of  matter — or  nothing 
whatever ! 


274 


TABLES   AND    NOTES 


355    E-Ss  3 
13*1   g£  fisgg   *   g      9   s 
ffSlijfcaJrtSJ    1    la    Sgg 


ii?I 


OO  J^ 

*5 


•lilallslxlj  Illl 


•*  os  I  o  »o'^o  od  t>  o  «o  o  I  I  o» 
io<xot-oco  io>>a»o  o 
«o<o»o-*o»»  eooo  -H 


si* 

j 

o 

a- 

5s 


'  ^  O5  OJ  <>»  O  »»  O  «  W>  O5  S<5  «  OS  <O  O  O>  t-     •«*     1-1  •*  CO  SO  10  i-c  00  !O  t-  **  « 
rt  I-  -H  («  -^c  ^-  -5.  («  10  «O  »  «O  r-l  >f)  t~  t~  O>  ^-  O<  OS  «O  00  S<5  O         <N  « 

i-H  i-H  i-l  I-H         rl  rH  i-(  i-H  T-I  M  (N 


<D—       »_T3  03  03       <D— i  i-  O  3  w      T3  cS  0)  3     «.,,-,       .    a>  u,  03X5— 

ffi   E  ,5  _<  £  fa 


:S 


•o 


!| 

:IJ  i 


si 


:c 


C     •     '.B 

I  :'ES 


l|e|ii^^iiijil|^|||llM  i  HsiS^Il 

I 


TABLES   AND    NOTES 


275 


sgssssisiggs 


276 


TABLES   AND    NOTES 


F. 


3500— 

-  6330 

3000— 

—  5400 

2800— 

—  5072 

2500— 

—  4532 

2225— 

—  4037 

2231- 

—  4000 

1710— 

—  3080 

1530— 

—  2731 

1400— 

-  2552 

1371— 

—  2500 

1200— 

—  2192 

1100- 

—  2012 

1063— 

—  1981 

1050- 

—  1922 

970- 

—  1778 

700- 

—  1292 

625— 

—  1157 

405- 

—  762 

400- 

-  752 

357- 

—  674 

316— 

-  600 

288- 

—  550 

215— 

—  420 

109— 

—  228 

100— 

-  212 

79- 

-  174 

65— 

—  149 

61- 

-  142 

46— 

—  114 

44- 

—  Ill 

40- 

-  104 

37.7— 

—  100 

36.8- 

-   98 

35— 

-   951 

30- 

-   86 

25- 

—   77 

20— 

-   68 

17- 

-   62 

15— 

-   59 

10- 

—   50 

5- 

-   41 

0— 

—   32 

-10- 

-   14 

-17.7- 

—   0 

-20- 

-   -4 

-38.8- 

-  34.3 

-40- 

-  -40 

-55— 

68 

-70— 

—  -94 

-100- 

-  -148 

-191— 

-  -312 

-252- 

422 

-257- 

-  -432 

-260- 

436 

-278- 

A 

459 

L 

THERMOMETER 


Temp,  of  electric  arc. 

Carbon  vaporizes. 

Temp,  attained  by  Thermit. 

Oxy-Hydrogen  flame. 

Osmium  melts. 

Iridium  melts. 

Heat  in  Bessemer  Furnace. 

Platinum  melts. 

Wrought  iron  melts. 

White  heat. 

Steel  melts. 

Orange-red  heat. 

Copper  melts. 

Pure  gold  melts. 

Cast  iron  (lowest)  melts. 

Silver  melts. 

Dull  red  heat. 

Aluminium  melts. 

(about)  Coal  ignites. 

Red-hot  iron  visible  in  dark. 

Mercury  boils. 

Lead  melts. 

Gunpowder  ignites. 

Tin  melts. 

Sulphur  melts. 

Water  boils. 

Alcohol  boils. 

Fusible  Alloy  melts. 

Beeswax  melts. 

Paraffin  melts. 

Phosphorus  melts. 


Human  body  in  health. 

Mean  temp,  of  sea. 
Mean  temp,  of  air  (London). 
Water  freezes. 
Mixture  salt  and  ice. 
Mercury  freezes. 

*Greatest  natural  cold  on 
earth  (antarctic). 

Sounding  balloon  (9  miles 
high). 

Air  liquefies  under  normal 
pressure. 

Hydrogen  liquefies. 

Hydrogen  freezes. 

Greatest  artificial  cold  pro- 
duced (Dewar). 

Absolute  zero. 


TABLES   AND    NOTES  277 

ELEMENTS  IN  CRUST  OF  EARTH 
WATER 

By  combining  a  large  number  of  analyses  of  rocks  of  all  sorts, 
F.  W.  Clarke  has  estimated  the  relative  amounts  of  elements  in 
the  crust  of  the  earth:  — 
Oxygen    ......   47.02  per  cent.      Manganese    ...     .07  per  cent. 

Silicon     ......  28.06        "  Sulphur    ......  07         " 

Aluminium    .  .     8.16        "  Barium   .......  05         " 

Iron  .........     4.64         "  Strontium    ...     .02 

Calcium    ......     3.50        "  Chromium    ...     .01         " 

Magnesium  ...     2.65         "  Nickel    ........  01         " 

Sodium   ......     2.63        "  Lithium  .......  01         " 

Potassium  ____     2.32        "      ^  Chlorine    ......  01         " 

Titanium    ....       .41         "       ML  Fluorine    ......  01         " 

Hydrogen    _____      .17        " 

Carbon    .......  12         "  100 

Phosphorus    .  .       .09         "  —  Science  Tear  Book,   1908. 

Mean  density  of  the  whole  earth  is  5.53  times  that  of  water. 

—  Science  Tear  Book,   1908. 

*  Capt.  Amundsen  reported  (in  1905)  a  temperature  of  — 
61.7°  C  (or  —  79°  F)  in  Boothia  (N.  Canada).  —68°  C  is  said 
to  have  been  experienced  in  Siberia. 

Fahrenheit  derived  his  scale  from  putting  zero  as  the  greatest 
cold  then  ascertained  (  by  mixing  salt  and  ice  )  .  The  temperature 
of  the  human  body  was  the  other  standard,  and  the  space  be- 
tween these  points  was  divided  first  duodecimally  into  24°  and 
later  into  one  quarter  of  this,  or  96°. 

Reaumur's  scale  (used  in  Germany)  divides  the  space  between 
the  freezing  and  boiling  points  of  water  into  80°. 

To  convert  these  scales  — 

F°  =      C°  +  32  =       R°  +  32 


R0  ^ 


278  TABLES   AND    NOTES 


THE   AIR 

1  cubic  foot  of  air  at  62°  F.  weighs  .076  Ibs.  (=  1.217  ozs.  or 
532.7  grains)  ;  at  32°  F.,  .08  Ibs.  1  litre  at  32°  F.  weighs  1293 
grammes.  13.141  cubic  feet  at  62°  F.  weigh  1  Ib. 

Normal  atmospheric  pressure  14.7  Ibs.  per  sq.  inch  =  2116.4 
Ibs.  per  sq.  foot.  A  column  of  mercury  30  inches  high  or  a 
column  of  water  33.947  ft.  is  supported. 

Sir  F.  Abel  and  Sir  A.  Noble  obtained  (in  researches  with 
explosives)  pressures  in  closed  steel  cylinders  up  to  95  tons  to 
the  square  inch. 

Air  expands,  or  contracts,  .002  of  its  volume  per  °  F. 

Air,  under  normal  pressure,  liquefies  at — 191°  C.  At  39 
atmosphere  pressures  it  will  liquefy  at — 140°  C. 

Liquid  air  occupies  %00th  the  volume  of  air. 

The  average  composition  of  normal  air  may  be  taken  as  fol- 
lows : — 


Vola. 

Nitrogen    769.5000 

Oxygen    206.5940 

Aqueous    vapour     14.0000 

Argon    9.3700 

Carbon    dioxide 0.3360 

Hydrogen     0.1900 

Ammonia    0.0080 

Ozone     0.0015 

Nitric   acid    .  0.0005 


1,000.0000 
Also- 


Neon    0.000014 

Helium    0.00000276 

Krypton    a  trace 

Xenon    .  a  trace 


TABLES   AND    NOTES 

SIZE    OF   MOLECULES 


279 


The   diameters  of  Molecules   have  been  ascertained  by  Jeans 
to  be— 

Hydrogen    20.3 

Nitrogen 29.1 

Oxygen 27.3 

These  figures  express  number  of  billionths  of  a  metre. 


METALLIC    SALTS 

These  are  formed  when  metals  replace  the  hydrogen  of  acids; 
or  when  acid-forming  oxides  combine  with  basic  oxides;  or  when 
metals  exchange  with  hydrogen  in  combining  an  acid  and  a 
hydroxide. 

If  all  the  hydrogen  is  replaced,  "  normal  salts "  are  formed ; 
if  part  is  left,  an  "acid  salt." 

Basic  salts  result  from  the  combining  of  a  normal  salt  with  a 
basic  oxide  or  hydroxide. 


CONDUCTIVITY   OF   METALS 


Substance. 

Heat 
Cond. 

Electrical 
Cond. 

Silver             

100.0 

100  0 

Copper 

73  6 

73  3 

Gold    

63  2 

58  5 

Aluminium      .    . 

31  3 

BO  5 

Brass 

23  6 

91    ^ 

Zinc     

19  9 

QQ  o 

Tin 

14  5 

99   R 

Iron  

11  9 

1Q     ft 

Lead    .  .    . 

8  5 

10  7 

Platinum    

6  4 

10   ^ 

Bismuth 

1  8 

1    Q 

Mercury    

1    R 

280  TABLES   AND    NOTES 

WATER 

Composition: — 2    vols.    Hydrogen    to    1    Oxygen.      Maximum 
density  at  4°  C.    (below  which  it  expands  slightly). 

Water  converted  to  steam  expands  to  1700  times  its  volume. 

Water  is  819.4  times  as   heavy  as  air. 

Composition  of  rain  water    (London)  : — 

Organic  Carbon...         .99  part  in  1,000,000  water. 
Organic    Nitrogen.         .22     "        "  " 

Ammonia 50     "         "  '*  " 

Nitrates  and  Nitrites     .07     "         "          "  " 

Chlorine     6.30     " 

Total   Solids 39.50     "         "          "  " 

COMMON   NAMES   OF    CHEMICALS 

Common  Names.  Chemical  Names  and  Formulae. 

Alum    Sulphate    of    Aluminium    and 

Potassium 

Aqua  Fortis Nitric  Acid,  HNO3 

Aqua    Regia Nitro-Hydrochloric  Acid 

Calomel    Mercurous  Chloride,  Hg2  C12 

Carbolic  Acid Phenol  C6H5OH 

Caustic  Potash Potassium  Hydrate  KOH 

Caustic    Soda Sodium  Hydrate,  NaOH 

Chalk   Calcium  Carbonate,  CaC08 

Copperas    Sulphate  of  Iron 

Corrosive  Sublimate Mercuric  Chloride,  HgCl2 

Cream  of  Tartar Potassium  Bitartrate 

Epsom  Salts Magnesium  Sulphate 

Ether    Diethyl  Oxide   (C2H5) 20 

Fire  Damp Light  Carburetted  Hydrogen 

Galena   Lead  Sulphide,  PbS 

Glauber's   Salt Sodium  Sulphate 

Glucose  or  Grape  Sugar Dextrose  C6H12O6 

Goulard   Water Basic  Acetate  of  Lead 

Iron  Pyrites Iron  Di-Sulphide,  FeS2 

Jewellers'    Putty Oxide  of  Tin 

Laughing  Gas Nitrous  Oxide,  NO 


TABLES   AND    NOTES  281 

COMMON    NAMES    OF  CHEMICALS— Continued 

Lime Calcium  Oxide,  CaO 

Lunar  Caustic Silver  Nitrate,  AgN08 

Mosaic  Gold Bi-Sulphide  of  Tin 

Muriatic   Acid Hydrochloric  Acid,  HC1 

Olefiant  Gas Ethylene,    C2H4 

Plaster  of  Paris Calcium  Sulphate 

Quartz    Silicon  Dioxide,  Si  O2 

Realgar    Arsenic  Di-Sulphide,  As     S. 

Red    Lead Oxide    of    Lead,    Pbg    O4 

Rochelle   Salt Sodium  Potassium  Tartrate 

Salammoniac    Ammonium  Chloride 

Salt,    Common Sodium  Chloride  NaCl 

Salt   of   Tartar Potassium  Carbonate 

Saltpetre   Potassium  Nitrate,  KNO8 

Salts  of  Lemon Oxalic   Acid 

Slaked  Lime Calcium   Hydrate 

Soda  Sodium  Carbonate 

Spelter  Zinc 

Spirits   of  Hartshorn Amm.  Hydroxide,  N4H.OH 

Spirits   of  Salt Hydrochloric  Acid,   HC1 

Sugar  of  Lead Lead  Acetate 

Tartar  Emetic Potass.  Antimony  Tartrate 

Verdigris  Basic  Copper  Acetate 

Vermilion    Sulphide  of  Mercury 

Vinegar    Dilute   Acetic   Acid 

Vitriol,    Blue Copper  Sulphate 

"         Green    Ferrous  Sulphate 

"        Oil  of Sulphuric  Acid,  H2SO4 

White Zinc  Sulphate 

Volatile    Alkali Ammonia 


282 


TABLES   AND    NOTES 

FREEZING   MIXTURES 


Ingredients. 


f  Snow  or  pounded  ice 

Chloride  of  sodium    (salt) 


Water 

Saltpetre    

Chloride    of     ammonium 
ammoniac)    


(  sal 


[Water 


Nitrate  of  ammonia. 


fWater 

4  J  Nitrate  of  ammonia 

Carbonate  of  soda 

(Snow 
Crystallized     chloride    of     cal 
cium  


[Crystallized   sulphate   of   soda. 
1  Hydrochloric  acid 

(Solid   Carbonic   Acid   dissolved 
in 
Sulphuric  ether 


16 
5 


20°C. 


26° 


45 


50° 


146 


EXPLOSIVES 
GUNPOWDEE   (English)  — 

Saltpetre     75  parts. 

Charcoal    15      " 

Sulphur    10      " 

Ground  to  fine  powder  and  intimately  mixed:  then  granulated. 
1  c.  in.  on  exploding  expands  to  800  c.  in.  of  gas. 


TABLES   AND    NOTES  283 

GUNCOTTON — Cotton  immersed  in  three  parts  sulphuric  acid 
(sp.  gr.  1.84)  and  1  part  nitric  acid  (sp.  gr.  1:52)  and  thor- 
oughly washed;  2£  to  4  times  as  powerful  as  gunpowder. 

NITRO-GLYCERINE  (Cg  Hg  Ng  Olg),  sp.  gr.  1.6 — 

Nitric  acid 1£  parts  by  wt. 

Sulphuric  acid... 2 

Glycerine  being  injected  into  the  mixture,  nitro-glycerine  floats 
to  the  top,  is  drawn  off,  washed,  and  filtered. 

Explodes  at  240°  to  300°  F.,  1  c.  in.  expanding  to  10,000  c.  in. 
of  gases,  or  about  10  to  13  times  as  strong  as  gunpowder. 

DYNAMITE — 3  parts  by  wt.  nitro-glycerine,  mixed  with  1  part 
Kieselguhr.  (infusorial  earth). 

BLASTING  GELATINE — Guncotton     dissolved    in  nitro-glycerine. 

COEDITE — Practically  the  same. 

PICBIC  ACID  (Lyddite,  Melinite,  etc.) — Carbolic  acid  treated 
with  nitric  acid. 

CHEMICAL   NOMENCLATURE. 

TERMINATION  " — UM"  is  now  applied  to  all  METALS, 
though  the  older-known  metals  retain  the  former  names,  e.  g. — 
Aluminium,  Tellurium,  etc. 

TERMINATION  "  — IDE  "  denotes  a  BINARY  COMPOUND,  that  is, 
a  substance  composed  of  only  two  elements,  e.  g. — Sodium  Chlo- 
ride (NaCl). 

TERMINATION  "  — OUS  "  is  applied  to  the  first  of  two  elements 
when  it  exists  in  a  greater  proportion  than  in  another  com- 
bination with  the  same  element,  e.  g. — one  atom  of  phosphorus 
and  three  atoms  of  chlorine  form  PHOSPHOROUS  CHLORIDE. 

TERMINATION  " — 1C,"  when  the  first  exists  in  a  lesser  pro- 
portion, e.  gr.— -one  atom  of  phosphorous  with  five  atoms  of 
chlorine  form  PHOSPHORIC  CHLORIDE. 

PREFIXES  —"MONO—,"  "  BI— ,"  "TRI— ,"  Ac.,  indicate  the 
proportion  of  the  latter  of  two  elements,  and  are  sometimes  used 
instead  of  the  above  termination.  Thus  phosphorus  chloride 
may  also  be  called  PHOSPHORUS  TRI-CHLOBIDE  ;  so  one  atom  of 
carbon  with  one  atom  of  oxygen  is  CARBON  MONOXIDE. 

PREFIX  —"HYPO—"  (under)  and  "PER—"  (over),  specify 
compounds  formed  by  the  same  two  elements  containing  less  (or 
more)  of  an  element  than  is  in  the  usual  compound. 

SESQUI — means  in  the  proportion  of  1  to  1^  or  2  to  3. 


284 


TABLES   AND    NOTES 


ALLOYS 

Bell    Metal =  4  copper,  1  tin. 

Brass    =  1  zinc,  2  copper. 

Bronze     (coins) =  95  copper,  4  tin,  1  zinc. 

German    Silver =  3  copper,  1  nickel,  2  zinc. 

Gold     (coinage  =  22    carats)*.  =  11  gold,  1  copper. 

Gold   ( Jeweller  s'=;  18  carats)..  =  3  gold,   1   copper. 

Gun  Metal =  9  copper,  1  tin. 

Invar    =  2  steel,  1  nickel. 

Magnetic    Alloy =  60     copper,     26     manganese,     14 

aluminium. 

Pewter    =  4  tin,  1  lead. 

Silver    (coinage) =  37  silver,  3  copper. 

Solder    (soft) =  lead  and  tin    (varies) . 

Solder    (hard) =  copper  and  zinc    (varies) . 

Speculum   Metal =  126.4  copper,  58.4  tin. 

Type  Metal =  4  lead,  1  antimony,  and  tin  (var.) 

WOOD'S  FUSIBLE   ALLOY 
Bismuth,   4   parts. 
Lead,  2  parts 
Tin,    1   part. 
Cadmium,  1  part. 

Melts  at  149°  F. 

METALLIC    OXIDES 
MONOXIDE  i=»  replacing  of  each  atom  of  hydrogen   in  H20  by  a 

monad,  or  both  by  a  dyad. 
HIGHER  OXIDES  =  replacing  of  hydrogen  atoms  in  molecules  of 

water  by  equivalent  atoms  of  metals. 
HYDEOXIDES  =  only    a    part    of    hydrogen    is    replaced    in    the 

water  molecules.    In  solutions  with  water  these 

have    alkaline   reaction. 
BASIC  OXIDES  and  HYDEOXIDES  form  salts  with  acids,  the  metal 

replacing  hydrogen. 
PEROXIDES,   and   ACID-FORMING  Oxides,  have  more  oxygen  than 

basic  oxides. 

*  Pure  gold  has  24  carats   ( of  240  grains )   in  a  Ib. 


INDEX 


Abel,  Sir  F.,  researches  of, 
with  explosives,  278 

Acetates  (see  also  Organic 
Acids),  223;  uses  of,  223; 
lead,  235,  280,  281 

Acids  (see  also  Organic 
Acids),  222;  essential  ele- 
ments in,  97;  nature  and 
qualities  of,  97;  elements 
contained  by,  97;  result  of 
action  of,  upon  a  base,  98 ; 
nature  of,  99;  action  of 
weak  and  strong,  99;  com- 
moner, 99 ;  examples  of,  in 
foods,  100;  taste  of,  100; 
chemical  definition  of,  100; 
hydrogen  chief  element  in 
defining  of,  101 ;  oxygen 
contained  by  most,  101 ; 
"trade  names"  of,  (refer 
tables) ,  102 ;  ordinary 
names  of,  101-102 ;  result  of 
combination  of,  with  a 
base,  104;  terminology  re- 
lating class  of,  with  specific 
salts,  105;  compounds  of 
non-metals  produce,  130 ; 
neutralized  by  ammonia 
(see  Ammonia),  188 

Acetic  Acid,  100;  ( see  <  also 
Organic  Acids),  223;  foot- 
note, 223;  dilute  (see  Vine- 
gar), 281 

Air,  9-15 ;  animals'  and  plants' 
need  of,  16 ;  how  to  secure 
perfectly  dry  and  pure,  19; 
composition  of,  37;  compo- 
sition of,  discovered,  263; 
composition  of  discovered 
(see  Cavendish),  264;  de- 


gree of  liquefaction  of,  un- 
der normal  pressure,  276; 
mean  temperature  of  (in 
London),  276;  (see  Table  of 
Elements),  278;  weight  of, 
278;  expansion  of,  278; 
contraction  of,  278;  lique- 
faction of,  278;  relative 
volume  occupied  by  liquid, 
278 ;  average  composition 
of  normal,  278;  volumes 
respectively  of :  Ammonia, 
Argon,  Carbon  dioxide, 
Helium,  Hydrogen,  Kryp- 
ton, Neon,  Nitric  acid, 
Nitrogen,  Oxygen,  Ozone ; 
in  normal,  278 

Alabaster,  125 ;  (see  also 
Calcium  sulphate),  203 

Albertus  Magnus,  281 

Albumen,  40;  (see  also  Car- 
bon compounds),  225 

Alchemysts,  origin  of  be- 
liefs of,  5 ;  testimony  con- 
cerning success  of,  results 
of  experiments  of,  men- 
tion of  history  of,  traces 
of  beliefs  of — in  chemical 
words,  metals  related  to 
planets,  in  beliefs  of,  7; 
mention  of,  261 

Alchemy,  origin  of  word,  to 
what  applied,  6 

Alcohols,  220-222;  meaning  of 
word,  221 ;  difference  be- 
tween ether  and,  222;  boil- 
ing point  of,  276 

Aldehydes  (see  Carbon  com- 
pounds), 221;  formula  for 
acetic  (footnote),  223 

Alkalies  (see  Sodium  Car- 
bonate), 197;  true  balance 


285 


286 


INDEX 


of— with  acids,  in  relation 
to  health,  10 ;  defined, 
tested,  10,5 ;  caustic  (see 
Ammonia),  188;  caustic 
potash  an  (see  Potassium 
hydroxide),  200;  chloral 
decomposed  by  (see  Chloro- 
form), 221 
Alkaline  properties,  elements 

possessing,  195 
Allotropism  defined,  92 
Alloys,  131-132 ;  table  of,  284 ; 
melting  point  of  fusible, 
276 ;  uses  of  silver,  139 ;  see 
also:  aluminium,  199,  284; 
antimony,  166,  284;  bis- 
muth, 184;  copper,  140-141, 
284;  gold,  284;  lead,  168, 
284  ;  manganese,  284 ;  man- 
ganese bronze,  181 ;  nickel, 
284;  silver,  284;  steel,  284; 
tin,  284;  zinc,  2&4;  Wood's 
fusible,  284;  proportions  of 
Bismuth  in,  proportions  of 
Cadmium  in,  proportions  of 
lead  in,  proportions  of  tin 
in,  284 

Alum,  179,  280;  uses  of,  179 
Aluminium  first  obtained, 
comparative  supply  of  in 
earth's  crust,  minerals  in 
which  is  found,  175;  orig- 
inal costliness  of,  history 
of  extraction  of,  175-6-7; 
production  of,  by  electro- 
lysis, 177;  properties,  quali- 
ties and  uses  of,  177-8;  pre- 
cious gems  mainly,  178; 
temperature  of  fusion  of, 
179;  glucinum  found  with, 
185;  melting  point  of,  276; 
see  also:  table  of  Valences 
in  Periodic  System,  255-7; 
Table  of  Elements,  274; 
Table  of  Alloys  (Magnetic 
Alloy),  284;  and:  alumin- 
ium bronze,  qualities  of, 
179;  aluminium  filings,  hy- 
drogen procured  by  use  of, 
179-180 ;  aluminium  sili- 
cate, pottery  clay  consists 


of,  179;  aluminium  sul- 
phate, 179 

Alumino-Thermics,   180 

Amalgams,  131 ;  Mercury,  171 

Amethyst  (see  Crystalline 
silica),  208 

Ammonia  (see  Volatile  al- 
kali), 281;  as  a  base,  com- 
bination of  elements  in, 
103;  acids  neutralized  by, 
103;  preparation  of,  186; 
properties,  qualities  and 
uses  of,  187-8-9;  volume  of, 
in  normal  air,  278;  propor- 
tions of,  in  rain  water,  280 ; 
hydroxide,  187;  (see  also 
Nitrogen  compounds  of), 
186-9  inch;  Nitrate  of  (see 
Freezing  mixtures),  282; 
(see  also  Priestley's  exper- 
iments), 263 

Ammonium  Chloride,  257 ; 
(see  also  Salammoniac), 
281 ;  Ammomium  group,188 ; 
Ammonium  Hydrate,  uses 
of,  189;  Ammonium  Hydro- 
oxide  (formula),  281;  (also 
Spirits  of  Hartshorn), 281; 
Ammonium  Sulphate,  188-9 

AmpSre,  274;  ammonium  dis- 
covered by,  267 

Amundsen,  Captain,  277 

Amylenes,  224 

Anesthetic,  ether  used  as, 
222 

Anilines  (see  Carbon  com- 
pounds), 224 

Aniline  Dyes,  40 

Anions,  as  non-metals  (see 
Experiments  in  Electro- 
lysis), 236 

Anode  (see  Faraday's  exper- 
iments in  electrolysis),  235- 
36 

Anthracite   (see  Coal),  90 

Antimony,  group  of  elements 
includes,  108;  effect  of 
Arsenic  combined  with,  in 
chlorine,  112;  uses  of, 
166;  uses  of  compared  with 
bismuth,  184;  uses  of  in 


INDEX 


287 


commerce,  167 ;  description 
of,  symbol  for,  thermopyle 
formed  by  bismuth  and, 
166 ;  proportions  of  in  type- 
metal,  284;  (see  also  Table 
of  Elements),  274 

Aqua  Fortis  (see  Nitric  acid), 
191-280 

Aqua  Regia,  134-280 

Arfordson,  274 

Argon,  21,  256,  274 

Arsenic,  group  of  elements 
includes,  108;  effect  of  an- 
timony combined  with  in 
chlorine,  112  ;  atomic  weight 
of  changed,  127j  descrip- 
tion of,  uses  of,  "symbol  of, 
165;  dangers  of,  symptoms 
of  poisoning  by,  166;  in 
Table  of  Chemical  Ele- 
ments, 274 

Arsenic  Di-Sulphide,  formula 
(see  Realgar),  281 

Asia,  Sodium  borate  found 
in,  199 

Astronomy,  why  scientific 
earlier  than  chemistry,  8 

Atmosphere,  elements  com- 
posing our,  in  order  of  their 
weights,  20 

Atom,  definition  of,  53 

Atomic  Theory,  what  made 
possible  by,  57;  (see  Boyle's 
Law),  262;  (see  Dalton's 
Law),  264;  acceptance  of, 
in  completer  form,  265 

Atoms,  molecules  made  up  of, 
64;  weight  of,  72-4-5;  ex- 
change of  in  compounds, 
268;  relation  of,  to  com- 
position of  matter,  273 

Atomic  Weights,  table  of, 
changed,  127 ;  standard  for 
finding,  of  elements,  245; 
Laws  of,  251-2 ;  ( see  Law 
of  Dulong  and  Petit),  251; 
relation  between  specific 
heat  and,  252;  (see  Exper- 
iments of  Dulong  and 
Petit) 

Avogadro,  Amadeo,  theory  of 


concerning      gases,      248-9, 

265 
Avogadro's   Law,   explanation 

of,  249 
Azote,  35 
Azotized,  35 


Bacon,  Roger,  261 

Baking  Soda  (see  Bicarbon- 
ate of  soda),  198 

Balard  (see  Bromines),  Table 
of  Chemical  Elements,  274 

Balloons,  process  of  prepar- 
ing hydrogen  for  (see  alu- 
minium), 180 

Bamboo,  silica  for  coating, 
209 

Barium,  184-5 ;  use  of,  in 
manufacture  of  paints,  use 
of  salts  of,  185;  calcium 
grouped  with,  203;  discov- 
ered, 266;  (see  also  Table 
of  Chemical  Elements), 
274 ;  (see  also  Table  of  Ele- 
ments of  Earth's  Crust), 
277 

Bases,  definition  of,  elements 
contained  in,  character  of, 
97;  result  of  action  of, 
upon  acids,  98,  104;  word, 
how  used  in  chemistry, 
103 ;  examples  of  acids 
neutralizing,  definition  of 
substance  of,  term  for  dis- 
tinguishing, 103 ;  metals 
combine  with  oxygen  and 
hydrogen  to  form,  130 

Basic  Salts,  279 

Beams,  preparation  of  steel 
for  building,  for  bridge, 
154 

Becquerel,  rays  from  uranium 
discovered  by,  271 

Beeswax,  melting  point  of, 
276 

Bell  Glass  (see  Priestley's 
Experiments),  263 

Bengal,  potassium  found  in, 
199 


288 


INDEX 


Benzol    (see  Coal-tar),  226 

Berthollet  (see  Law  of  Defin- 
ite Proportions),  264 

Beryllium  (see  Glucinium), 
185;  and  Table  of  Ele- 
ments, 274 

Berzelius,  selenium  discov- 
ered by,  126;  (see  Theories 
of  combination  of  gases), 
265-8;  (see  Theory  of  bin- 
ary combinations),  267-8; 
(see  also  Table  of  Chemi- 
cal Elements),  274-5 

Bessemer   (see  Steel),  152 

Bessemer  Furnace,  heat  in, 
276 

Bessemer  Process,   152 

Bi  (prefix)  in  chemical  no- 
menclature, 283 

Bicarbonate   of   Soda,   198 

Binary  Combinations,  theory 
of,  267-8 

Binary  Compounds,  termina- 
tion denoting,  283 

Bismuth,  color  of,  130;  de- 
scription of,  comparative 
weight  of,  uses  of,  in  medi- 
cine, 184;  (see  also  Table 
of  Chemical  Elements), 
274;  (see  also  Table  of 
Conductivity  of  Metals), 
279 

Black,  Carbonic  acid  gas  dis- 
covered by,  263 

Black  Phosphorus,  prepara- 
tion of,  192 

Blast  Furnace,  diagram  of, 
147 

Blasting  Powder,  Chili  salt- 
petre used  in,  199 

Blue  Vitriol  (see  also  Copper 
Sulphate),  141 

Boisbandran  (see  Atomic  wts. 
of  Gallium  and  Samarium), 
274-5 

Borax  (see  Sodium  borate), 
199;  description  of,  for- 
mula for,  laboratory  uses 
of,  general  uses  of,  oxides 
dissolved  by,  207;  (see  also 
sodium  salt),  207 


Boric  Acid,  where  occurring, 
207 

Boron,  carbide  of  (footnote), 
89;  weight  of,  changed, 
127;  description  of,  206; 
silver  classed  with,  208; 
(see  also  Table  of  Chemi- 
cal Elements),  274 

Boyle,  demonstration  of,  con- 
cerning gases,  248;  relation 
to  modern  chemistry  of, 
259;  true  analysis  of  sub- 
stances begins  with,  262 

Boyle's  Law,  262 

Brandt  (see  Phosphorus  and 
Cobalt,  Table  of  Chemical 
Elements),  274-5 

Brass,  Table  of  Conductivity 
of  Metals,  279 

Bridge  Beams,  preparation  of 
steel  for,  154;  (see  Iron 
and  Steel,  processes  of 
manufacture  of) 

Bromide,  of  potassium,  112- 
113,  201;  use  of,  in  medi- 
cine, 113-201 ;  use  of,  in 
photography,  201 ;  of  silver, 
use  of,  113;  (see  also  Sil- 
ver), 138 

Bromine,  group  of  Halogens 
includes,  108 ;  atomic  weight 
of,  two  ways  of  preparing, 
chlorine  combined  with, 
sodium  combined  with,  112 ; 
action  of,  description  of, 
effect  of,  uses  of,  deriva- 
tion of  name,  discovered, 
113;  (see  also  Table  of 
Elements),  274 

Bronze   Age,   139-144 

Bronze  (see  Copper),  139- 
142 ;  aluminium  (see  alu- 
minium), 179;  bronze  man- 
ganese (see  manganese), 
181;  bronze  alloy  (coins), 
Table  of  Alloys,  284 

Building,  beams  (see  pro- 
cesses of  steel  manufac- 
ture), 154;  cements  (see 
limestone),  204;  limes,  204 

Bunsen     (see     Caesium     and 


INDEX 


289 


Rubidium,  Table  of  Chemi- 
cal Elements),  274-5 

Burning,  as  known  in  chem- 
istry, 18;  nature  of,  in 
gases  other  than  oxygen, 
93 ;  as  instance  of  chemical 
action,  227 

Butane  (see  Alcohols),  220, 
224 

Butter,  225 

Butylenes  (see  Butanes,  Al- 
cohols), 224 


Cadmium,  characteristics, 
symbol  of,  uses  of,  173 

Cadmium  Sulphide  (see  Cad- 
mium, uses  of),  173 

Caesium,  195 ;  discovered  by 
spectroscope,  properties  of, 
202;  (see  also  Table  of 
Chemical  Elements),  2~74 

Calcic  Sulphate,  uses  of,  206 

Calcium,  sodium  borate  in 
compounds  with,  199 ;  sym- 
bol of,  a  metal,  203;  dis- 
covered, 266 ;  ( see  also 
Table  of  Chemical  Ele- 
ments), 274;  (see  also  Ta- 
ble of  Elements  in  Earth's 
Crust),  277;  and  Freezing 
Mixtures,  Crystallized 
Chloride  of,  282 

Calcium  Carbide,  Acetylene 
gas  derived  from,  205 

Calcium  Carbonate  (see  Ex- 
periments of  Cavendish), 
264;  formula  of  (see 
Chalk),  280 

Calcium  Chloride,  Affinity  of, 
for  water,  mercury  artifi- 
cially frozen  by  combina- 
ation  of,  with  snow,  206 

Calcium  Hydrate  (see  Slaked 
lime,  Table  of  Common 
Names),  281 

Calcium  Hydroxide,  symbol 
of  (see  Slaked  lime),  205 

Calcium  Light  (see  Quick- 
lime), 205 


Calcium  Oxide,  symbol  for, 
205;  (see  Lime,  Table  of 
Common  Names),  281 

Calcium  Sulphate  (see  Plas- 
ter of  Paris,  Table  of  Com- 
mon Names),  281 

Calico  Printing,  borax  used 
in,  207 

California,  sodium  borate 
found  in,  199 

Calomel  (see  Mercurous 
Chloride,  and  formula  of, 
Table  of  Common  Names), 
280 

"Calx  of  Mercury"  (see 
Priestley's  Experiments ) , 
263 

Cannon,  steel  prepared  for 
(see  Processes  of  Steel 
manufacture),  154 

Carbide  of  Boron,  89  (note)  ; 

Carbolic  Acid,  280;  use  of, 
in  Picric  Acid,  283 

Carbon,  nature  of,  81-82 ;  im- 
portance of  to  human  life, 
combination  of,  with  oxy- 
gen, 84;  compounds  of,  86- 
87,  213-226;  where  found 
pure,  substances  of  which, 
is  essential  part,  87;  quali- 
ties of,  88;  three  forms  of, 
89 ;  theory  concerning  dif- 
ference in  forms  of,  91 ;  in- 
cluded in  group  of  ele- 
ments, 108 ;  chlorine  does 
not  combine  readily  with, 
112;  atomic  weight  of, 
changed,  127 ;  relative 
amounts  of,  in  wrought  and 
cast  iron,  and  in  steel,  149; 
comparative  importance  of, 
in  organic  life,  208;  dis- 
tinction of,  from  other  ele- 
ments, 213;  compound  of 
hydrogen  with  (see  Hydro- 
carbon), 215-216;  result  of 
hydrogen  combined  with, 
218;  study  of,  brought 
about,  267;  temperature  of 
vaporization  ( Thermome- 
ter), 276;  proportions  of 


290 


INDEX 


in  rain  water  (Table),  280; 
(see  also  Table,  Periodic 
System),  255-8;  (see  also 
Table  of  Elements  on 
Earth's  Crust),  277 

Carbon  Atoms,  linking  of,  214 

Carbon  Boride  (see  Iron),  206 

Carbon  Compounds,  213-226; 
concerning  theories  of,  226 

Carbon  Di-Oxide,  dough 
raised  by,  198;  action  of 
water  containing  (see 
Limestone),  203;  experi- 
ments with,  264 ;  ( see  also 
Carbon  Compounds),  218 

Carbon  Di-Sulphide,  how 
formed,  uses  of,  125 

Carbon  Filaments,  in  electric 
lighting,  tungsten  filaments 
compared  with  (see  Elec- 
trical work),  183 

Carbon  Monoxide  (see  Car- 
bon compounds),  218 

Carbonates,  of  alkalies,  263; 
of  lithium,  202;  of  potas- 
sium, 201 ;  of  soda  ( see 
Freezing  Mixtures),  282 

Carbonic  Acid  Gas,  discovery 
of,  263 

Carborundum,  209 ;  product  of 
electric  furnace,  232-3 

Carnelian  (see  Crystal  sili- 
cate), 208 

Cast  Iron   (see  Iron),  146-7 

Cathode  (see  Faraday's  ex- 
periments with  electrolysis), 
235 

Cations,  metals  as  (see  Fara- 
day's experiments  with 
electrolysis),  236 

Caustic  Potash  (see  Potas- 
sium hydroxide),  200;  (see 
also  Table  of  Common 
Names),  280 

Caustic  Soda  (see  Table  of 
Common  Names),  280 

Cavendish,  Henry,  263 ;  re- 
searches and  discoveries  of, 
264;  (see  also  Hydrogen, 
Table  of  Chemical  Ele- 
ments), 274 


Cements  (see  Uses  of  sili- 
cates), 209;  (see  Lime- 
stone, building  lime),  204; 
hydraulic,  Portland,  Rosen- 
dale,  205 

Ceylon,  potassium  found  in, 
199 

Cerium,  Table  of  Chemical 
Elements,  274 

Chalk,  formations  of,  chalk 
cliffs  (see  England),  204; 
(see  also  Table  of  Common 
Names),  280 

Chemicals,  Divisions  of,  97; 
Tables  of  Common  Names 
of,  280 

Chemical  Action,  227-243;  re- 
lation of,  to  forms  of  en- 
ergy, 229;  modern  benefits 
from  study  of,  229;  origin 
of  laws  of,  253 

Chemical  Aflinity,  qualities 
known  as,  94 

Chemical  Combinations,  Na- 
ture of,  93-106 

Chemical  Compounds,  use  of 
saltpetre  in,  201 

Chemical  Elements,  Symbols 
of,  69-70;  table  of,  274-5 

Chemical  Equations,  correct, 
71 ;  value  of,  recorded,  72-3 

Chemical  Formulae,  system  of 
letters  and  numbers  for 
(see  Berzelius),  265 

Chemical  Law,  245 

Chemical  Nomenclature,   283 

Chemical  Processes,  wonders 
of  modern,  228 

Chemical  Study,  attempts  to 
systematize,  269-70 

Chemical  Symbols,  value  of, 
72 

Chemistry,  as  a  mature 
science,  8;  what  is  of 
practical,  85;  part  of  ni- 
trogen in  "organic,"  part 
of  nitrogen  in  inorganic, 
40;  distinct  from  physics, 
67;  foundation  of  modern 
(see  Boyle),  76-7;  story  of, 
261-284 ;  way  to  conquest  of 


INDEX 


291 


"  organic  ",  opened,  267 ; 
sciences  of  electricity  and, 
united,  266;  Liebig's  re- 
searches in  agricultural, 
267 

Chalcedony  (see  Crystalline 
silica),  208 

Charcoal,  nature  of,  28-9; 
method  of  burning  sub- 
stances into,  29;  how  ob- 
tained, 85;  (see  oxygen), 
burned  by  nitric  acid,  190; 
proportions  in  gunpowder 
of,  282 

Chili,  sodium  nitrate  found  in, 
199 

Chili  Saltpetre  (see  Chili), 
199 

Chloral    (see  Alcohols),   221 

Chlorides,  silver  (see  Silver), 
138;  ferric  (see  Ferric 
Salts),  156;  in  solution,  in 
chemical  tests,  241 

Chloride,  of  ammonium  (see 
Freezing  Mixtures),  282; 
of  magnesium  (see  Table 
Salt),  196;  of  radium,  271 

Chlorine,  sodium  and  phos- 
phorus burn  in,  30 ;  propor- 
tion of,  in  salt,  75 ;  combi- 
nation of,  with  hydrogen, 
93;  in  group  of  Halogens, 
108-9;  defined,  109;  descrip- 
tion of,  effect  of,  uses  of, 
separation  of,  from  common 
salt,  110;  efficacy  in  disin- 
fecting and  bleaching,  111 ; 
atomic  weight  of,  effect  of, 
upon  burning  charcoal,  112 ; 
experiments  of  Dumas 
with,  208;  proportion  of,  in 
rain  water  (see  Table), 
280;  (see  also  Table,  Peri- 
odic System),  255-7  (and 
Tables),  274,  277 

Chlorine  Gas,  elements  that 
burn  in,  112 

Chloroform  (see  Alcohols), 
221 

Chrome  Alum,  uses  of,  182 

Chromium,  description  of,  ex- 


traction of,  compounds  of, 
effect  upon  steel ;  182-3  (see 
also  Tables),  274-77 

Chrome  Yellow,  182 

Cinnabar  (see  Mercury  Sul- 
phide), use  of,  to  artists, 
119;  (see  Mercury),  170; 
two  forms  of,  171 

Cider,  "Mother  of  Vinegar" 
in,  223 

Citric  Acid  (see  Organic 
acids),  223 

Clarke,  F.  W.,  relative 
amounts  of  elements  esti- 
mated by,  277 

Claus  (see  Ruthenium,  Ta- 
ble), 275 

Clay  (see  Silicates),  209; 
pottery  (see  Aluminium 
Silicate),  179 

Cleansing  Agents  (see  Borax) , 
207 

Cleve  (see  Thulium,  Table), 
275 

Coal,  importance  of,  79;  or- 
igin of,  80-81,  85 ;  result  of 
distillation  of,  81;  bitu- 
minous, lignite,  90;  point 
of  ignition  of  (Thermome- 
ter), 276 

Coal  Gas,  apparatus  for 
manufacture  of,  83 

Coal  Tar  (see  Carbon  Com- 
pounds), 224-225-226 

Cobalt,  discovery  of,  descrip- 
tion of,  affinity  of  oxygen 
for,  effect  of  heat  on  salts 
formed  by  combinations  of, 
variety  of,  in  pure  state, 
salts  formed  by  combina- 
tions of,  157;  uses  of,  in 
arts,  158;  included  in 
platinum  group,  164;  (see 
also  Table),  274 

Coke,  how  made,  91 

"  Century's  Progress  in  Chem- 
istry, The"  (see  Williams), 
266 

Cold,  greatest  natural,  degree 
of,  greatest  artificial,  de- 
gree of  (Thermometer), 276 


292 


INDEX 


Combustion,  nature  of  (see 
Priestley's  Experiments ) , 
263;  (cf.  combustible  and 
oxidizable),  18 

Compounds,  classification  of, 
how  fixed,  96-7-8;  acid, 
base,  107 

Converter  (see  Bessemer 
process),  152-3 

Copper,  vapor  of  sulphur  com- 
bined with,  93;  color  of, 
130;  amounts  of,  found 
pure,  131 ;  ancient  discov- 
ery and  use  of,  139 ;  ( see 
Copper  Age)  ;  atomic  weight 
of,  chemical  symbol  for,  de- 
rivation of,  name  of,  specific 
gravity  of,  140;  alloys  of, 
140-1 ;  properties,  qualities, 
uses,  compounds  of,  140-2; 
two  classes  of  compounds 
of,  141 ;  pigments  derived 
from,  carbonate  of,  142; 
use  of,  in  coloring  glass, 
210;  (see  also  Tables  of: 
Periodic  System),  255-8; 
(Chemical  Elements),  274; 
(Conductivity  of  Metals), 
279;  (see  Blue  Vitriol), 
Common  Names  of  Metals, 
281;  Alloys,  284;  melting 
point  of,  276;  acetate  (see 
Verdigris),  142-281 

Copper  Age,  139-144 

Copper  Compounds,  danger- 
ous, chief  uses  of,  142 

Copper  Vessels,  danger  of, 
for  food,  142 

Copperas  (Table  of  Common 
Names),  280 

Coquina,   204 

Cordite  (see  Blasting  Gela- 
tine, Explosives),  283 

Corrosive  Sublimate  (see 
Mercury  Chloride),  uses  of, 
171;  Table  of  Common 
Names,  280 

Corundum  (see  Oxides  of 
Aluminium),  178 

Courtois  (see  Iodine,  Table 
of  Chemical  Elements),  274 


Cream  of  Tartar  (see  So- 
dium), 198;  how  formed, 
224;  (see  Potassium  bitar- 
trate,  in  Table  of  Common 
Names),  280 

Crondstadt  (see  Nickel,  Ta- 
ble of  Chemical  Elements), 
275 

Crookes  (see  Thallium,  Table 
of  Chemical  Elements),  275 

Crown  Glass   (see  Glass), 211 

Crystalline  Silica,  208 

Cupric  (see  Copper  com- 
pounds), 141 

Cuprous  (see  Copper  Com- 
pounds), 141 

Cuprous  Oxide,  symbol  for, 
uses  of,  142 

Curi£  (see  Radium,  Table  of 
Chemical  Elements),  275 

Cyanide  of  Potassium  (see 
Potassium  Cyanide),  201 


D 


Davy,  Sir  Humphrey,  175; 
composition  of  salt  proved 
by,  196;  experiments  of,  in 
electrolysis,  235;  union  of 
chemical  and  electrical 
sciences  begins  with,  266; 
(see  also  Table  of  Chemical 
Elements),  274-5;  (in  re: 
boron,  barium,  calcium, 
magnesium,  sodium,  potas- 
sium, strontium) 
Dalton,  John,  10-11-15;  re- 
searches of,  10;  biographi- 
cal sketch  of,  11 ;  discovery 
of,  concerning  elements  in 
combination,  16;  theory  of, 
245 ;  demonstration  concern- 
ing gases,  248 ;  theories  first 
put  forth  by,  264 
Decay  (see  Oxidizing),  28 
Del  Rio  (see  Vanadium),  275 
"  Dephlogisticated  Air"  (see 

Oxygen),  263 

Deville,    Ste.    Claire,    alumin- 
ium prepared  by,  175 


INDEX 


293 


Dextrose  (see  Glucose,  or 
Grape  Sugar,  Table  of  Com- 
mon Names),  280 

Diamond,  nature  of,  81 ;  Mois- 
san's  electric  furnace  for 
making,  90-1  (see  Carbon 
Boride),  206;  (see  Prepara- 
tion of  Carborundum ) ,  233 ; 
(hardness  of  Carborundum 
compared  with) 

Diethyl  Oxide  (see  Ether, 
Table  Common  Names),  280 

Dioxide  (Carbon)  (see  Car- 
bonate of  Copper),  142 

"  Disassociation,"  theories  of 
atomic,  269 

Disinfectants  (see  Formalin), 
221;  (see  Lime),  205 

Dolomite  deposits  of  (see 
Magnesium  Calcium  Car- 
bonate), 174 

Double  Decomposition,  de- 
fined, 94 

"  Drummond  "  Light  (see  Cal- 
cium Light),  205 

Drying  Agents  (see  Calcium 
chloride),  206 

Dulong,  experiments  of,  266 

Dulong  and  Petit,  Law  of, 
251 

Dumas,  demonstration  of,  267- 
68;  in  relation  to  theory  of 
compounds,  270 

Dyes,  aniline,  40 

Dyeing,  acetates  used  in,  223; 
borax  used  in,  207;  Glaub- 
er's Salt  used  in,  199 

Dynamite  (see  Explosives), 
283 


Earth,  foundation  of  crust  of, 
21 

Earths,  Alkaline,  263 

Electricity,  bromine  separated 
from  bromides  by,  112 ;  met- 
als conductors  of,  130;  ap- 
plication of  magnetization 
in  mechanical  electricity, 
155;  uses  of  platinum  in 


handling  of,  162;  carbon 
filaments  compared  with 
Tungsten  in  electrical  ap- 
paratus, 183;  action  of,  on 
organic  life,  216;  solutions 
which  conduct,  240 

Electric  Action  (see  Elec- 
trons), 63 

Electrical  Apparatus,  short 
circuits  prevented  (see  Bis- 
muth), 184 

Electric  Arc,  Temperature  of 
(see  Thermometer),  276 

Electric  Batteries,  copper  sul- 
phate useful  in,  141 ;  use  of 
zinc  in,  172 ;  use  of  hydro- 
chloride  in,  188 

Electric  Current,  action  of, 
42-3 

Electric  Machine,  120 

Electrode  (see  Electrol,  Fara- 
day's experiments),  236 

Electrolysis,  233-238;  alumin- 
ium extracted  by  177;  dis- 
covery of,  233 ;  experiments 
in,  234-5 ;  measurement  of 
electric  current  in,  236;  re- 
lation of  metals  and  non- 
metals  in,  236;  measure- 
ment of  work  of  electric 
current  in,  237;  theoretical 
explanation  of,  238;  rela- 
tion of  disintegration  of 
atoms  to,  253 

Electrolyte  (see  Electrolysis, 
Faraday's  experiments),  235 

Electrons,  Sir  Oliver  Lodge  in 
regard  to,  59-60;  how  elec- 
trified, movement  of,  61 : 
freeing  of  negative,  63; 
atoms  made  up  of,  64 ;  hypo- 
thetical ly  not  matter,  66; 
in  radio-active  bodies,  273 

Electro-Plating,  232 

Elements,  replaced  by  "prin- 
ciples," 9 ;  theory  of  simple, 
50;  proportion  of,  in  com- 
pounds, 73;  Table  of  fre- 
quent, Table  of  rarer,  75; 
Dal  ton's  discovery  concern- 
ing proportions  of,  76;  the 


294 


INDEX 


four  great,  84-5 ;  number  of, 
96 ;  commoner,  groups  of, 
107-127 ;  non-metal  group 
of,  107;  group  of,  in  chem- 
istry, 108;  proportions  of, 
indicated  in  atomic  weight, 
116;  metallic,  128-211;  com- 
parative weights  of  (see 
Chemical  Law),  245;  "com- 
bining weight"  of  (see 
Chemical  Law),  246;  pro- 
portionate weights  of  (see 
Chemical  Law),  246-7)  ;  re- 
lation in  ordering  of  (see 
Periodic  Law),  253-4;  val- 
ency of,  defined,  254-6; 
named  according  to  valency, 
256;  variations  of  propor- 
tions of,  257;  Dr.  Wollas- 
ton's  demonstration  con- 
cerning, 265 ;  limit  to  com- 
bination of,  illustrated,  268 ; 
Table  of  Elements  in 
Earth's  Crust,  277 

Elihrjar,  d'  (see  Tungsten, 
Table  of  Chemical  Ele- 
ments), 275 

Elixir  of  Life,  9 

Emerald  (see  Aluminium  sili- 
cate), 178;  Glucinum  found 
in),  185 

Emery  (see  Oxides  of  Alu- 
minium), 178 

Enamel,  borax  used  in  manu- 
facture of,  207 

Energy,  relation  of  chemical 
action  to  forms  of,  229,  230- 
231 ;  heat,  example  of  tak- 
ing up  of,  light,  example  of 
taking  up  of,  231 ;  electric, 
examples  of  taking  up  of, 
231-2 

England,  chalk  cliffs  in,  204 

Epsom  Salts  (see  Magnesium 
Sulphate ) ,  125-174 ;  ( see 
also  Table),  280 

"  Equivalents,"  elements  com- 
bine in,  253,  257 

Erbium  (see  Table),  274 

Etching,  Nitric  acid  used  in, 
190 


Ethane  (see  Hydrocarbons, 
218,  220,  224),  formula  for 
(footnote),  223 

Ether,  Atmospheric,  motions 
of,  61-2 

Ether  (Diethyl  oxide),  how 
prepared,  uses  of,  222;  Ta- 
ble of  Common  Names,  280 

Ethyl  (see  Alcohols),  radicals 
forming,  220 

Ethyl  Alcohol,  in  preparation 
of  ether,  222 ;  formula  for 
(footnote),  223 

Ethylene  (see  Carbon  com- 
pounds), 218;  Table  of 
Common  Names  (Olefiant 
gas),  281 

Explosives,  given  by  nitrogen, 
40 ;  use  of  saltpetre  in,  201 ; 
Sir  A.  Noble's  and  Sir  F. 
Abel's  researches  with,  278  ; 
Table  of,  282-3 


F 


Fahrenheit,       derivation      of 

scale  of,  277 
Fats,  ether  used  to   dissolve, 

222 

Faraday,  work  of,  in  experi- 
ments with  electrolysis,  235 ; 

Law   of    (see  Electrolysis), 

237 
Feldspar   (see  Silicates),  199, 

209 

Ferric  Hydroxide,  155 
Ferric  Salts,  colors  of,  156 
Ferrous  Sulphate    (see  Green 

Vitriol,    Table   of    Common 

Names),  281 
Fertilizer,  use  of  gypsum  as, 

206;   use   of   lime  as,  205; 

use   of   sodium    nitrate   as, 

199 
Fire,  as  affect  of  oxygen  on 

matter,    18;    ancient    ideas 

of,  227;  story  of  chemistry 

begins  with  use  of,  261 
Fire-Dnmp      (see     Methane), 

218-219;   Table  of  Common 

Names,  280 


INDEX 


295 


Fireproofing,  silicates  used  in, 
209 

Flint  (see  Crystalline  silica), 
208 

Florida,  Coquina  in,  204 

Fluorine,  group  of  Halogens 
includes,  108 ;  description 
of,  atomic  weight  of,  hydro- 
fluoric acid,  compound  of, 
114;  characteristics  of,  oxy- 
gen does  not  combine  with, 
115;  weights  of,  group,  in 
order,  116;  atomic  weight 
of,  changed,  127;  Table  of 
Chemical  Elements,  274 ; 
Table  of  Elements  in 
Earth's  Crust,  277 

Food  Preservatives  (see 
Borax),  207 

Food  Stuffs,  Liebig's  improve- 
ments in,  267 

Formaldehyde  (see  Forma- 
lin), 221 

Formalin  (see  Aldehydes) 
221 

Formic  Acid,  221 

Franklin,  Benjamin,  aid  of, 
to  Priestley,  262 

Freezing  Mixtures,  Table,  282 

Fruit  Juices,  elements  con- 
tained in,  87 


G 


Gahn  (see  Manganese,  Table 
of  Chemical  Elements),  2T4 

Gas,  Acetylene  (see  Carbon 
compounds),  205;  prepara- 
tion of,  219 ;  hydrogen  com- 
bined with,  218;  production 
of,  232;  Illuminating,  how 
derived,  84 

Gases,  recently  discovered  in 
air,  list  of  rare,  in  atmos- 
phere, 20-1 ;  combining  of 
(footnote),  76-7;  theory  of 
pressure  of,  consistency  of, 
248;  volume  of,  253;  rare, 
256 ;  discovery  of  weight  of, 
264;  combination  of  (see 
Gay-Lussac),  265 


Gas-Metal  (see  Radium ),  255- 
58 

Gay-Lussac,  265,  274;  dis- 
covery of  cyanogen  by, 
267 

Gadolinium,  Table  of  Chemi- 
cal Elements,  274 

"  Galena"  (see  Lead),  167, 
169;  lead  sulphide  named, 
119;  Table  of  Common 
Names,  280 

Gallium,  258 ;  Table  of  Chemi- 
cal Elements,  274 

Garnet,  silicate  of  alumin- 
ium contained  by,  178 

Gelatine,  Blasting  (see  Ex- 
plosives), 283 

Germanium,  258;  Table  of 
Chemical  Elements,  274 

German  Silver  (see  Table  of 
Alloys),  284 

Germany,  Reaumur's  scale 
used  in,  277 

Glass  (see  Silicon),  209-211; 
process  of  whitening,  182; 
uranium  used  for  coloring, 
183-4;  fused  quartz  used 
as,  water,  209;  colored, 
flint,  Bohemian,  first  made, 
210;  annealing  of,  iron 
oxide  in,  211 ;  making  of 
plate,  210 

Glass  Making,  Glauber's  Salt 
used  in,  198;  Carbonate  of 
potassium  used  in,  201 ; 
borax  used  in,  207 

Glauber's  Salt  (see  Sodium 
sulphate),  198,  125;  Table 
of  Common  Names,  280 

Glucinum,  how  found,  de- 
scription of,  salts  of,  185 

Glucose  (see  Grape  Sugar, 
Table  of  Common  Names), 
280 

Gold,  130,  135 ;  atomic  weight 
of,  134;  properties,  quali- 
ties and  uses  of,  132-3-4-5, 
210;  symbol  of,  134;  melt- 
ing point  of  pure  (Ther- 
mometer), 276;  (see  also 
Tables  of  Periodic  System), 


296 


INDEX 


255-8 ;  ( Chemical  Elements ) , 
274;  (Alloys),  284 

Goulard  Water  (see  Basic 
Acetate  of  Lead  (Table), 
280 

Graphite,  nature  of,  81; 
compared  with  diamond,  89 

Green  Vitriol  (see  Iron  Sul- 
phate), 125 

Gun  Cotton  (see  Explosives), 
283 

Gun  Metal,  Table  of  Alloys, 
284 

Gunpowder,  199;  as  example 
of  unstable  compounds,  230 ; 
igniting  point  of  (Ther- 
mometer), 276;  (see  also 
Table  of  Explosives),  282 

Gypsum  (see  Calcic  Sul- 
phate), 125,  203,  206 

H 

Hall,  Process,  aluminium  ex- 
tracted by,  177 

Halogens,  Group  of,  108;  de- 
rivation of  word,  109 

Harper's  Magazine  (see  Arti- 
cle by  Henry  Smith  Wil- 
liams), 266 

Hartshorn  Spirits  (see  Am- 
monia), 187 

Hatchett  (see  Tantalum,  Ta- 
ble of  Chemical  Elements), 
275 

Heat,  influence  of,  in  forming 
new  bodies,  10;  Robert 
Boyle  in  relation  to  influ 
ence  of,  10 ;  metals,  conduc- 
tors of,  130 ;  a  sign  of  mo- 
tion, relation  of,  to  chemical 
action,  229-232;  effect  of, 
on  molecular  motion,  248; 
degree  of  orange  red,  of 
dull  red  (see  Thermome- 
ter), 276 

Helion,  21 

Helium,  256,  272;  (Table  of 
Chemical  Elements),  274 

Herman  (see  Cadmium,  Table 
of  Chemical  Elements),  274 

Hinrichs,   270 


Hisinger  (see  Cerium,  Table), 
274 

Hjelrn  (see  Molybdenum,  Ta- 
ble of  Chemical  Elements), 
274 

Horn  Silver,  136 

Human  Body,  Temperature 
of,  in  health  (Thermome- 
ter), 276 

Hydraulic  Cement,  205 

Hydrates,  103;  Sodium,  Ta- 
ble of  Common  Names,  280 ; 
ferric  (see  Ferric  Salts), 
156 

Hydrocarbons,  216;  (see  Com- 
pounds of  Carbon),  218-220 

Hydrochloric  Acid  (see  also 
Muriatic  Acid  and  Spirits 
of  Salt,  Table),  281;  pro- 
duction of,  93;  result  of 
zinc  combined  with,  93-4; 
use  of,  to  dissolve  gold, 
134;  (see  also  Freezing 
Mixtures),  282 

Hydrochloric  Acid  Gas,  meth- 
ods of  obtaining,  111 

Hydrochloride,  uses  of,  in 
electric  batteries,  188 

Hydrofluoric  Acid,  use  of,  in 
the  arts,  glass  corroded  for 
etching  by,  114;  density  of, 
combination  of,  with  met- 
als, elements  that  unite 
with,  oxygen  does  not  unite 
with,  115 

Hydrogen,  12 ;  experiments 
with,  24;  theory  of,  com- 
parative weight  of,  47-48; 
as  unit  of  weight,  48-49; 
theory  concerning,  65-66 ; 
attraction  of  oxygen  for,  95  ; 
freezing  of,  by  sodium,  196 ; 
method  of  releasing,  200; 
lithium  unites  with,  202; 
combination  of  carbon  with, 
215-216;  Priestley's  experi- 
ments with,  263;  Table  of 
Chemicals,  274 ;  freezing 
point  of  (Thermometer), 
276)  ;  liquefying  point  of 
(Thermometer),  276;  Ta- 


INDEX 


297 


ble  of  Elements  of  Earth's 
Crust,  277;  diameter  of 
molecules  of  (Table),  279; 
Light  Carburetted  (see 
Fire-damp,  Methane),  280; 
(Table),  Sulphuretted,  122 

Hydroxides,  103;  method  of 
formation  of,  200;  metallic, 
replaced  by  radicals  (see 
Alcohols),  221;  (see  Metal- 
lic Oxides,  Table  of  Alloys), 
284 

Hydroxyl  (see  Radicals  form- 
ing alcohols),  220;  see 
Preparation  of  ether),  222; 
see  Ionic  theory  of  neu- 
tralization), 242 

Hypo  (prefix),  (see  Chemical 
Nomenclature),  283; 
"hypo"  (see  Sodium  thio- 
sulphate),  138 

Hypo  Sulphite  of  Soda,  use 
of,  125 


Ic  (Termination)  (see  Chemi- 
cal Nomenclature),  283 

Ice,  Temperature  of  mixture 
of  salt  and  (Thermometer), 
276)  ;  pounded  (see  Freez- 
ing Mixtures),  282 

Iceland  Spar   (see  Calcium) 

Illuminating  Gas,  presence  of 
ethylene  in,  219 

Incandescent  Electric  Lights, 
use  of  Tungsten  in,  183 

Infusorial  Earth  (see  Kiesel- 
ghur),  283 

Inks,  what  combined  to  make, 
156 

Inorganic  Compounds,  silicon 
foundation  of,  258 

Invar  (see  Table  of  Alloys), 
284 

"Invisible  College,"  262 

Iodides,  action  of,  114 

Iodine  (see  Halogens),  108; 
atomic  weight  of,  113;  ef- 
fect of  heat  upon,  uses  of, 
vapor  of,  compared  with 


air,  solutions  of,  effect  of 
combination  of,  with  phos- 
phorus, uses  of,  in  medicine, 
114 ;  in  compound  of  iodo- 
form,  222;  (see  Table  of 
Chemical  Elements),  274 

lodoform    (see  Alcohols),  222 

Ions  (see  Electrolysis,  Fara- 
day's experiments),  236 

Ionic  Theory,  neutralization 
explained  by,  242 

Iridium,  hardness  of,  130; 
(^ee  Description  of  plati- 
num), 161;  platinum  group 
includes,  uses  of,  164;  (see 
Table  of  Chemical  Ele- 
ments), 274;  melting  point 
of  (see  Thermometer),  276 

Iron,  especially  treated  of, 
143-157;  vapor  of  sulphur 
combined  with,  93 ;  benefit 
to  mankind  of,  143-4;  steel, 
as  form  of,  144;  uses  of, 
144-8;  rarity  in  pure  state, 
145;  where  plentiful,  146; 
ores  of,  146;  difference  be- 
tween cast  and  wrought, 
148-9;  Bessemer  process  of 
converting,  152 ;  processes 
removing  other  elements 
from,  153 ;  magnetization 
of,  qualities  of,  154;  im- 
portance of  manner  of  mag- 
netization of,  155;  effect  of 
moisture  upon,  effect  of 
iron  rust  in  relation  to 
electricity,  manner  of  pro- 
tection of,  155;  platinum 
group  includes,  164;  red 
hot,  visible  in  dark,  degree 
of  heat  of  (Thermometer), 
276;  (see  also  Table:  Chem- 
ical Elements),  274;  (Ele- 
ments in  Earth's  Crust), 
277;  (Conductivity  of 
Metals),  279;  (Common 
Names),  280;  cast,  146-7; 
melting  point  of  cast,  276; 
pig,  146;  wrought,  quali- 
ties and  uses  of,  process  of 
making,  advantages  of,  over 


298 


INDEX 


cast,  148-9;  process  of  add- 
ing carbon  to  wrought  (see 
Bessemer),  152;  melting 
point  of  wrought  (see 
(Thermometer),  276 

Iron  Age,  144 

Iron  Compounds,  where  found, 
145-6;  two  general  classes 
of,  155-6;  main  uses  and 
value  of,  157 

Iron  Industry,  uses  of  lime- 
stone in,  204 

Iron  Pyrites  (see  Table  of 
Common  Names),  280 

Isomerism,   269 

Isomorphism,  discovery  of, 
266 


Jasper        (see       Crystalline 

silica),  208 
Jeans,  diameter  of  molecules 

ascertained  by,  Table,  279 
Jeweler's     Putty,     Table     of 

Common  Names,  280 


Kelvin,  Lord,  analogy  of 
atomic  theory,  58 

Kieselghur,  Proportions  in 
dynamite,  Table  of  Explos- 
ives, 283 

Kirchloff  (see  Caesium,  Table 
of  Chemical  Elements),  274 

Klaproth  (see  Titanium,  Ta- 
ble of  Chemical  Elements), 
275 

Krypton,  21,  256;  Table  of 
Chemical  Elements,  274 


Lactic  Acid  (see  Organic 
Acids),  100,  223 

Lanthanum,  Table  of  Chemi- 
cal Elements,  274 

Lavoisier  (see  Azote),  name 
given  by,  40;  explanation 
of  composition  of  water,  41 ; 
(see  Oxygen  and  composi- 
tion of  air),  262-3 


Laughing  Gas  (see  Nitrous 
oxide),  189;  Table  of  Com- 
mon Names,  280 

Law  of  Octaves  (see  John 
Newlands),  270 

Lead,  hardness  of,  130;  de- 
scription of,  symbol  for, 
ores  of,  processes  of  ex- 
traction from  ores,  167; 
comparative  weight  of,  167- 
68;  uses  of  alloys  of,  com- 
mercial uses  of,  monoxides 
of,  salts  of,  168;  Sugar  of, 
169 ;  relation  of  to  uranium, 
273;  (see  Table  of  Chemi- 
cal Elements),  274;  point 
of  fusion  of  (see  Ther- 
mometer), 276;  Table  of 
Conductivity  of  Metals, 
279;  Table  of  Alloys,  284; 
Acetate  of  (see  Decomposi- 
tion, experiments  in  Elec- 
trolysis), 235;  (see  Goul- 
ard Water,  Sugar  of  Lead, 
Table  of  Common  Names), 
280-1 ;  Commercial,  where 
derived,  167 ;  red,  uses  of, 
168;  white,  169;  chromate, 
182;  sulphide  (see  Galena), 
280;  (Table  of  Common 
Names) 

Leather,  how  preserved,  196 

Lenses  (see  Plate  Glass),  210 

Leyden  Jar,  234 

Liebig,  Studies  and  achieve- 
ments of,  267 ;  discovery  of 
isomerism  by,  269 

Life,  Organic  agencies  affect- 
ing, interchange  of  sub- 
stances in,  216 

Light,  hypothesis  concerning 
origin,  63;  action  on  or- 
ganic life,  216;  chemical 
combinations  producing, 
230 ;  effect  of,  on  unstable 
compounds  of  silver  in 
photography,  231 

Light  Rays,  new  kinds  of 
(see  "  Fourth  State  of  Mat- 
ter)," 65 

Lime    (see    Calcium    Oxide), 


INDEX 


299 


uses  of,  properties  of,  how 
obtained,  slaked,  205;  (see 
Table  of  Common  Names), 
281 

Limes,  for  building,  204 

Limestone,  dissolution  of,  203 

Lime  Water  (see  Calcium 
hydroxide),  205 

Liquids,  character  of,  acid 
and  alkaline,  9-10 

Liquid  Metal  (see  Mercury), 
255-8 

Lithium,  195;  properties  of, 
comparative  weight  of,  202 ; 
(see  Table  of  Periodic  Sys- 
tem), 255-7;  (Table  of 
Chemical  Elements),  274; 
( Elements  in  E  a  r  t  h's 
Crust),  277 

Lithium  Carbonate,  use  of, 
202 

Litmus  Paper,  defined,  use  of, 
99;  alkalies  tested  by,  103; 
effect  of  solutions  of  salt 
upon,  104 

Lockyer  (see  Table),  274 

Lodge,  Sir  Oliver,  59-60; 
hypothesis  of,  concerning 
hydro-electrons,  59-60 

Lulli,  Raymond,  261 

Lunar  Caustic,  137-8;  (Table 
of  Common  Names),  281 

Luray  Cavern,  204 

Lyddite  (see  Picric  Acid,  Ta- 
ble of  Explosives),  283 


M 


Magic,  relation  of  history  of 
chemical  action  to,  relation 
of  properties  of  elements 
to  ideas  of,  228 

Magnesium,  symbol  for,  173; 
abundance  of,  melting  point 
of,  properties  of,  174;  (see 
Glucinum,  185 ;  Tables,  255- 
57,  277;  phosphates  of,  174; 
calcium  carbonate,  174 ; 
oxide,  use  of  in  medicine, 
174;  sulphate  (see  Epsom 
Salts),  125;  uses  of  Com- 


pounds of,  174;  Table"  of 
Common  Names,  280;  oxide 
(Magnesia),  174 

Magnetic  Alloy,  Table  of  Al- 
loys, 284 

Magnetization,  of  iron,  of 
steel,  154 

Malic  Acid  (see  Organic 
Acids),  223 

Mammoth  Cave,  204 

Manganates  (see  Manganese), 
181 

Manganese,  atomic  weight, 
127;  uses  of,  weight  of, 
point  of  fusion  of,  180-2; 
(see  Sodium  borate),  199; 
(see  also  Tables),  274,  277, 
284 

Marignac  (see  Table),  275 

Marsh  Gas  (see  Methane), 
218 

Matter,  two  kinds  of  divis- 
ions of,  13 ;  defined  by  phys- 
ics, constantly  divisible, 
51;  "fourth  state"  of, 
"dead"  theory  of,  64-5; 
three  states  of,  247 ;  Boyle's 
view  of,  262 

Meat,  elements  contained  in, 
87;  cured  (see  Rock  Salt), 
196 

Mendeleef,  Improvement  of 
Periodic  System  by,  254-5; 
new  substances  predicted 
by,  258-9,  270 

Melinite  (see  Picric  Acid* 
Explosives),  283 

Mercuric  Chloride  (see  Cor- 
rosive Sublimate,  Table), 
280 

Mercurous  Chloride  (see  Calo- 
mel, Table),  280 

Mercury,  atomic  weight  of, 
changed,  127 ;  description 
of,  ores  of  (see  Cinnabar), 
symbol  of,  uses  of  in  medi- 
cine, uses  of  amalgams  of, 
physiological  effect  of,  170- 
71-2;  artificially  frozen, 
206;  boiling  and  freezing 
points  of  (Thermometer), 


300 


INDEX 


276;  conductivity  of  (Ta- 
ble), 279;  (see  also  Tables), 
255-8,  275 ;  fulminating, 
171-2;  iodide,  uses  of,  171; 
chloride,  uses  of,  171 

Metalfic  Salts,  279 

Metals,  beliefs  of  alchemists 
regarding,  7-8 ;  elements 
forming  bases,  ranked  with, 
97 ;  early  definition  of,  128 ; 
distinction  of,  'from  non- 
metals,  modernly  defined, 
129;  white,  129-30;  colors 
of,  129-30;  combination  of 
oxygen  with,  130;  combina- 
tion of  hydrogen  and  oxy- 
gen with,  130;  qualities  of, 
compounds  or  ores  of,  mix- 
tures of  (see  also  Alloys), 
variation  of  specific  gravity 
of,  extraction  of,  from 
ores,  found  in  pure  form, 
130-1 ;  earliest  use  of,  261 ; 
terminology  applied  to,  283 

Meteorites,  iron  in  pure  state 
in,  145;  occurrence  of 
nickel  in,  159 

Methane  (see  Carbons,  hydro- 
carbons), 218,  220,  224 

Methyl  Alcohol  (see  Carbon 
compounds,  Alcohols,  radi- 
cals forming),  219-220 

Meyer,  improvement  of  Peri- 
odic System  by,  254,  270 

Mica   (see  Silicates),  209 

Milk,  225 

Milk  of  Lime  (see  "White- 
wash)," 205 

Minium  (see  Red  lead),  168 

Moissan,  experiments  of,  with 
diamonds,  88-9 ;  electric 
furnace  of,  90-1 

Molecular  Weight,  meaning 
of,  251 ;  means  of  finding, 
240;  (see  Solutions) 

Molecules,  definition  of,  52; 
matter  made  up  of,  64; 
formula  for,  70-1 ;  move- 
ments of,  in  gases,  247-8; 
proof  concerning,  268;  re- 
lation of,  to  composition  of 


matter,  273;  Table  of 
diameters  of,  279;  com- 
pound, theory  of,  265 

Molybdenum  (see  Chromium), 
183,  276 

Monad  (see  Units  of  Val- 
ency), 214 

Mono  (prefix)  (see  Chemical 
Nomenclature),  283 

Monoxides  (see  Metallic  Ox- 
ides, Table),  284 

Mordants,  Alums  known  as, 
179 

Mosaic  Gold  (Tables),  274 

Mosander   (see  Table),  274-5 

"Mother  of  Vinegar"  (see 
"Organic  Acids),"  223 

Multiple  Proportions,  Law  of, 
76 

Muriatic  Acid  (see  Hydro- 
chloric acid),  111 


N 


"Natural  Gas"  (see  Me- 
thane) 

"  Negative  Gravity  "  (see  Me- 
thane), 263 

Neodymium    (Table),  275 

Neon  (Table),  275;  and  pp. 
21,  256 

Neutral  Substances,  all  salts 
not,  104 

Neutralization,  Ionic  theory 
of,  242 

Newell's  "Descriptive  Chemis- 
try," Formulas  from,  223 

Newlands,  Periodic  Law  sug- 
gested by,  254;  also,  270 

Niagara  Falls  (see  Manufac- 
ture of  Carborundum),  233 

Nickel,  valuable  quality  of, 
in  manufacturing,  alloys  of, 
158;  (also  see  Table  of  Al- 
loys ) ,  284 ;  properties  of, 
cf.  w.  iron,  occurrence  of 
in  pure  state,  159;  Tables, 
275,  277 

Niobum  (see  also  Columbum, 
Table),  275 


INDEX 


301 


Nitrate,  potassium,  189,  199, 
200,  281;  silver,  137,  138; 
sodium,  189,  199 ;  strontium, 
185 

Nitrates  and  Nitrites,  propor- 
tion of,  in  rain  water  (Ta- 
ble), 280 

Nitric  Acid  (see  Compounds 
of  Nitrogen ;  also  see  Aqua 
fortis),  use  of,  to  dissolve 
gold,  134;  preparation  of, 
formula  for,  189-90 ;  sodium 
nitrate  used  in  making, 
199;  analysis  of,  by  Caven- 
disb,  263-4;  (see  also  Ta- 
ble), 280;  Explosives,  283 

Nitrogen,  combined  with  oxy- 
gen, 16;  modification  of 
oxygen  by,  27 ;  means  of 
obtaining  free,  proportions 
of  atoms  in,  35;  properties 
of,  use  of,  in  nature,  36; 
bow  readily  prepared,  38; 
discovered,  absorbed  by 
plants,  fertilization  of  soil 
by,  39;  compounds  given 
rise  to  by,  in  organic  cbern- 
istry,  in  inorganic  chemis- 
try, 40;  in  group  of  ele- 
ments, 108;  compounds  of, 
185-191;  how  obtained,  185- 
86;  lithium  unites  with, 
202 ;  addition  of,  to  hydro- 
carbons, 216 ;  experiments 
of  Priestley  with,  263;  Ta- 
bles, 275,  279,  280 

Nitroglycerine  (see  Explos- 
ives), 283 

Nitro  Hydrochloric  Acid  (see 
Aqua  Regia,  Table),  280 

Nitrous  Oxide,  189;  (Table), 
280 

Noble,  Sir  A.,  researches  of, 
with  explosives,  278 

Non-Metals,  elements  known 
as,  97,  109;  early  definition 
of,  129 ;  compounds  of,  130 

Normal  Salts  (see  Table), 
279 

O 

Oersted,    Compound    of    chlo- 


rine and  aluminium  made 
by,  176 

Oils,  ethers  used  to  dissolve, 
222 

Olefiant  Gas  (see  Ethylene), 
218,  281 

Olive  Oil,  225 

Organic  Chemistry,  way  to 
conquest  of,  276 

Osmic  Acid,  256 

Osmium  *  (see  Description 
Platinum),  161;  uses  of, 
164 ;  Table,  256 ;  Thermome- 
ter, 276 

Opal   (see  Silica),  208 

Organic  Acids,  222 

Organic  Chemistry,  268 

Organic  Compounds,  217 ;  car- 
bon as  foundation  of,  258 

Organisms,  chief  elements  en- 
tering into,  215 

Ous  (termination)  (see  Chemi- 
cal Nomenclature),  283 

Oxalic  Acid  (see  Organic 
Acids),  223;  (see  Salts  of 
Lemon),  281 

Oxides,  how  produced,  com- 
parative weight  of  with  air, 
28 ;  combination  of  oxygen 
and  metals  form,  130 ;  acid- 
forming,  basic,  higher,  me- 
tallic, Table,  284;  copper, 
142;  ferric  (see  Ferric 
Salts),  156;  iron,  27;  lead, 
281  (Table)  ;  tin  (Table), 
280 

Oxidize,  18 

Oxidizing,  equivalent  to  burn- 
ing, 31 

Oxydizing  Agents  (see 
Chromium),  182 

Oxygen,  agent  in  changes, 
combined  with  nitrogen, 
meaning  of  name,  16; 
comparative  amounts  of,  re- 
ceived by  man  and  creat- 
ures, 17;  hibernating  ani- 
mals need  of,  18;  where 
found  especially,  21 ;  literal 
meaning  of,  method  of  ob- 
taining by  itself,  discovery 


302 


INDEX 


of,  22;  experiments  with, 
24 ;  made  commercially, 
method  of  obtaining,  prop- 
erties of,  25;  readiness  to 
combine  with  other  ele- 
ments, 26;  heat  and  light 
caused  by  action  of,  27 ;  ac- 
tion of,  upon  blood,  29; 
condensed,  32;  atom  of,  as 
standard  of  weight,  50; 
strong  attraction  for  hydro- 
gen, experiment  with,  95-6; 
groups  of  elements  includ- 
ing, 108;  element  that  does 
not  combine  with,  115 ;  sul- 
phur group  includes,  116; 
atomic  weight  of,  126-7 ;  af- 
finity of  cobalt  for,  157; 
action  of  on  potassium,  200 ; 
lithium  unites  with,  202; 
abundance  of  (see  Silicon), 
210 ;  effect  on  hydrocarbons, 
216;  discovered,  263;  Ta- 
ble, 277;  diameter  of  mole- 
cules of,  279 

Oxy  hydrogen  Flame  (Ther- 
mometer), 276 

Ozone,  31 ;  expansion  of,  con- 
densation of,  32;  discov- 
ered, most  abundant  in,  as 
a  disinfectant,  as  an  oxi- 
dizer,  produced  in  thunder- 
storm, 33 


Palladium  (see  Metals  in  ore 
of  Platinum),  161;  cf.  prop- 
erties of  platinum,  163; 
laboratory  use  of,  platinum 
group  includes,  164 ;  Table, 
275 

Paracelsus,  261,  275 

Paraffin,  melting  point  of 
( Thermometer ) ,  276 

Paraffin  Series  (see  Hydro- 
carbons), 218,  220 

Paris  Green  (see  Organic 
Acids),  223 

Pasteur,  267 


Pearlash  (see  Carbonate  of 
Potassium),  201 

Peat  (see  also  Coal),  90 

Pentane,   224 

Per  (prefix)  (see  Chemical 
Nomenclature),  283 

Periodic  Law,  Explanation  of 
Table  of,  254-6 

Periodic  System,  Elements 
classified  by,  213 ;  relations 
in  valency  demonstrated  by, 
257 ;  Table  of,  259,  270 

Permanganates  (see  Manga- 
nese), of  potassium,  uses  of, 
181 

Peroxides  (see  Metallic  Ox- 
ides, Table),  284 

Petit,  experiments  of,  266; 
Dulong  and,  Law  of.  251 

Petrified  Wood  (see  Silica), 
208-9 

Phenol  (see  Carbolic  Acid, 
Table),  280 

Pewter,  170;  alloy  of  (see 
Table),  284 

"  Philosopher's  Stone,"  9 

Phlogiston,  263 

Phosphates,  necessity  of,  for 
fertilization  of  soil,  19,  23 

Phosphorus,  combines  with 
oxygen,  27,  30 ;  group  of  ele- 
ments includes,  108;  chlo- 
rine melts  and  burns,  112; 
effect  of  combination  with 
iodine,  114;  preparation  of 
red,  yellow,  black,  respect- 
ively, forms  of,  characteris- 
tics of,  where  found,  uses 
of,  191-2 ;  frequency  of, 
217;  melting  point  of  (Ther- 
mometer), 276;  (Tables), 
255-7,  275,  277 

Photographic  Lenses  (see 
Silicon),  200 

Photographic  Operations,  use 
of  litmus  paper  in,  100 

Photography,  Chemistry  of, 
138;  effects  of  light  on  un- 
stable compounds  of  silver 
in,  231 ;  spectra  studied  by, 
270-1 


INDEX 


303 


Physics,  function  of,  realm 
of,  as  distinguished  from 
chemistry,  54-5 

Picric  Acid  (see  Explosives), 
283 

Pig  Iron    (see  Iron),  146 

Pigments,  acetates  used  in 
making,  223 

Pitchblende,  "  rays "  abund- 
ant in,  271 ;  proportions  of 
radium  and  uranium  in, 
273 

Plaster  of  Paris,  125,  281 

Plate  Glass,  210 

Platinum,  161-5 ;  description 
of,  derivation  of  name  of, 
rare  metals  contained  in 
ore  of,  161 ;  process  of  pre- 
cipitating, 161-162;  labora- 
tory use  of,  use  of  in  elec- 
trical manipulation,  162 ; 
general  uses  of,  162-3 ;  "  oc- 
clusion "  of,  163 ;  proper- 
ties of,  163-4;  crucibles  for 
melting,  205;  melting  point 
of  (Thermometer),  276; (see 
also  Tables),  275,  279 

Platinum  Group,  properties 
of,  elements  in,  164-5 

Platinum  Paper,  20 

Platinum  Wire,  laboratory 
use  of,  207 

Pneumatic  Trough,  23  (see 
also  Priestley),  263 

Polonium,  273;  (see  also  Hel- 
ium), 273 

Potash  (see  Carbonate  of  Po- 
tassium), 201 

Portland  Cement,  205 

Potassium,  acids  neutralized 
by,  103;  compounded  with 
chromium,  182,  195;  occur- 
rence of,  symbol  of,  salts 
of,  description  of,  extrac- 
tion of,  test  for  presence  of, 
as  pure  metal,  200,  202; 
silicates  of,  209;  experi- 
ments of  Sir  H.  Davy  with, 
266;  Tables,  275.  277;  Anti- 
mony Tartrate  (see  Tartar 
Emetic,  Table),  281;  Bi- 


tartrate  (see  Cream  of  Tar- 
tar), 280;  bromide,  bromine 
extracted  from,  112:  bro- 
mide, use  of  in  medicine, 
113;  Carbonate  (see  Salt  of 
Tartar,  Table),  281;  chlo 
rate,  201 ;  cyanide,  uses  of, 
201 ;  hydrate  (see  Caustic- 
Potash,  Table),  280;  hy- 
droxide, uses  of,  200; 
nitrate,  use  of  in  prepara- 
tion of  nitric  acid,  189;  ni- 
trate, sodium  nitrate  used 
in  making,  199;  nitrate  (see 
Saltpetre,  Table),  281;  sul- 
phate, 179;  uses  of,  201 

Pottery,  three  classes  of  (see 
Aluminium  silicate),  179 

Pottery  Clay  (see  Aluminium 
silicate),  179 

Praseodymium,    Table,    275 

Precious  Stones,  making  arti- 
ficial (see  Flint  Glass), 
210 

Precipitate,  definition  of,  96 

Preservatives  (see  Formalin), 
262 

Priestley,  262,  263,  275;  ex- 
periments of,  263 

Propane  (see  Hydrocarbons), 
218,  220,  224 

Proportions,  combining  of 
elements,  245 ;  Law  of 
Definite,  76 ;  idem,  245,  264 ; 
Law  of  Multiple,  245  (see 
Dalton),  264 

Propyl  (see  Alcohols,  radicals 
forming),  220 

Propylenes,  224 

Proust  (see  Law  of  Definite 
Proportions),  76,  264,  270 

Pyrites  (see  Iron) 

Q 

Quartz  (see  Silicates),  208; 
fusion  of,  209 ;  Table,  281 

R 

Radicals,  effect  of  occurrence 
of,  in  Carbon  compounds, 
217-218;  relation  of,  to  bin- 
ary combinations,  267,  268 


304 


INDEX 


Radio- Active  Bodies,  Elec- 
trons in,  273 

Radio-Activity,    explained,   63 

Radium  (see  Radio-activity), 
63 ;  weight  of,  changed,  127 ; 
Table,  Periodic  System, 
255-8;  three  kinds  of  rays 
of,  272 ;  proportions  of 
uranium  and,  in  pitch- 
blende (see  Pitchblende), 
272 ;  Table  of  Chemical 
Elements,  275 

Rails,  preparation  of  steel 
for  (see  Steel),  154 

Rain,  measure  of  fall  (Dai- 
ton's  experiments),  11 

Ramsay  (see  Table),  274-5 

Rayleigh  (see  Table),  274 

Realgar  (see  Table),  281 

Reaumur,  scale  of,  277 

Red  Lead  (see  also  Lead  and 
Minium,  Table),  281 

Red  Phosphorus  (see  also 
Phosphorus),  191-2 

Refrigerating  Agents  (see 
Calcium  Chloride),  206 

Reich  (see  Table),  274 

Reichenstein,  Tellurium  dis- 
covered by,  126;  Table,  275 

"Reversibility"  of  Chemical 
Compounds,  Theories  of, 
269 

Rhodium  (see  Platinum),  161- 
64;  Table,  275 

Richter,  Table,  274 

Rochelle  Salts,  198-281 

Rock  Crystal  (see  Crystalline 
silica),  208 

Rocks  formed  by  shells,  204; 
(see  Coquina) 

Rock  Salt,  deposits  of,  meat 
cured  by,  leather  preserved 
by,  196 

Rontgen  Rays,  discovery  of, 
271 

Rose,  Table,  275 

Rosendale  Cement  (see  Ce- 
ments), 205 

Royal  Society,  262 

Ruby  Glass,  210 

Rubidium,  discovery  of,  prop- 


erties  of,   202;   Table,   195, 

275 
Russia,    Platinum    ore    found 

in,  161 
Rust   (see  Ferric  hydroxide), 

of  iron,  of  zinc,  of  copper, 

27 

Rusting,  cause  of,  26 
Ruthenium,    description,    161 ; 

Platinum     group     includes, 

164;  Table,  275 
Rutherford,    Nitrogen    discov- 
ered by,  39 ;  Table,  275 


S 


Safety  Plugs  (see  Bismuth, 
uses  of),  184 

Salammoniac  (see  Table), 
281;  (Freezing  Mixtures), 
282 

Saleratus  (see  Baking  Soda), 
198 

Salt,  Chemical  Name  of,  104; 
Glauber's,  125;  chloride  of 
magnesium  in,  196;  (see 
sodium  chloride),  196;  (see 
also  Thermometer),  276; 
Table,  281;  Metallic  Salts 
(Acid  Salt),  279;  (see 
Salts) 

Saltpetre  (see  also  Nitrate  of 
potassium),  200-1;  nitrogen 
part  of,  35;  Table,  281; 
Explosives,  282 

Salts,  Constituents  of,  97; 
solubility  of,  distinguished 
as  "  neutral,"  104 ;  acid, 
125,  279;  basic,  279;  Ep- 
som, 125;  ferric  and  fer- 
rous, 155-6;  metallic  (see 
Table),  279;  normal,  125; 
(see  Table),  279;  of  lemon, 
281;  of  potassium,  199;  of 
tartar,  Table,  281 

Samirium    (see  Table),  275 

Scandium,   258,  275    (Table) 

Sand    (see   Silicates),  208 

Scheele,  Chlorine  first  pre- 
pared by,  110 


INDEX 


305 


Schmidt,  Rays  from  thorium 
discovered  by,  271 

Schroder   (see  Table),  274 

Science,  its  two  divisions  of 
development,  50 

"  Science  Year  Book,"  data 
from,  277 

Scientific  Practice,  defined, 
56-7 

Sea,  Mean  temperature  of 
(Thermometer),  276 

Seaweed,  Sodium  carbonate 
prepared  from,  197 

Seidlitz,  198 

Selenides,   116 

Selenite  (see  Calcium  sul- 
phate), 203 

Selenium,  group  of  elements 
includes,  108 ;  sulphur 
group  includes,  116;  symbol 
of,  125 ;  use  of  in  elec- 
tricity, discovery  of,  atomic 
weight  of,  character  of,  two 
forms  of,  126;  (see  also 
Table),  275 

Sesqui  (see  Chemical  Nomen- 
clature), 283 

Silica,  glucinum  found  with, 
185 ;  potassium  combined 
with,  199 ;  example  of  fam- 
ily of,  208 

Silicates,  209 

Silicon,  group  of  elements  in- 
cludes, 108 ;  comparative 
importance  of,  207;  abund- 
ance of,  208-210;  (see  Peri- 
odic System,  Table  of), 
255-8;  Table,  277;  carbide 
(see  Carborundum),  209, 
233;  dioxide  (see  Quartz), 
208;  Table,  281. 

Silver,  properties  of,  135; 
specific  gravity  of,  com- 
parative value  of,  propor- 
tions of  purity  of,  effect  of 
sulphur  upon,  ores  of, 
mines  of  in  U.  S.,  136;  pro- 
cesses in  mining,  136-7; 
oxidized,  136;  alloys  of, 
139;  Table  of  Alloys,  284; 
Table,  275;  melting  point 


of,  Thermometer,  276;  Con- 
ductivity of,  Table,  279; 
(also  see  Table  Per.  Sys.), 
255-8 ;  bromide  of,  113,  138 ; 
chloride  of,  136,  138;  ni- 
trate of,  how  formed,  137, 
138;  combinations  of  in 
photography,  138;  use  of, 
in  electrical  experiment  (see 
Electrolysis),  234;  (see  also 
Lunar  Caustic,  Table),  281 

Sirius,  271 

Slaked  Lime,  making  of,  uses 
of,  205-6;  Table,  281 

Slate    (see  Silicate),  209 

Smalt   (see  Cobalt),  157-8 

Smith's,  A.,  "  General  Inor- 
ganic Chemistry  "  (see  Law 
of  Atomic  Weights),  250, 
252 

Snow  (see  Freezing  Mix- 
tures), 282 

Soaps,  Carbonate  of  potas- 
sium used  in  making,  201 ; 
borax  combined  with,  207; 
yellow  (see  silicates),  209, 
225 

Soda,  Caustic  (see  Sodium 
hydroxide),  197;  Table, 
281 

Sodium,  30;  proportion  of  in 
salt,  75;  acids  neutralized 
by,  103;  hardness  of,  130; 
description  of,  comparative 
weight  of,  symbol  for,  pro- 
portion in  earth's  crust, 
195;  apparatus  for  manu- 
facture of,  197;  experi- 
ments of  Sir  H.  Davy  with, 
266;  (see  also  Tables),  255- 
57,  277;  Compounds,  ex- 
pense of,  202;  borate,  uses 
and  properties  of,  199;  car- 
bonate, 197,  and  Table,  281 ; 
chloride,  196;  and  Table, 
281;  Hydrate  (see  Caustic 
Soda,  Table),  280;  hydrox- 
ide, 197;  (Natrium,  Table), 
275 ;  nitrate,  use  of,  in  prep- 
aration nitric  acid,  189 ; 
where  found,  199;  oxide, 


306 


INDEX 


peroxide,  197 ;  potassium 
(see  Rochelle  Salt,  Table), 
281;  salt,  207;  silicates, 
209;  sulphate,  125;  symbol 
for,  198;  (see  Glauber's 
Salt,  Table),  280;  thio-sul- 
phate,  125 ;  use  of,  in  pho- 
tography,  138  (see  "hypo")  ; 
tungstate  (see  Chromium), 
183 

Solder,  170;  soft  (see  Alloys, 
Table),  284 

Solids,  most  bases  are,  103; 
total,  in  rain  water,  Table, 
280 

Solutions,  early  theory  con- 
cerning, 238;  modern  dis- 
coveries in,  238-9 ;  non-con- 
ducting and  conducting, 
240-1-2;  Summary  of  theory 
of,  243,  253;  ions  and  ca- 
tions in,  273 

Sounding  Balloon  (see  Bal- 
loon) 

Specific  Gravity  (see  Table 
Per.  Sys.),  255-258 

Specific  Heat,  defined,  251; 
relation  between  atomic 
weight  and,  252 ;  reasons 
for  law  of,  253 ;  Dulong 
and  Petit's  experiments, 
206 

Spectra,  examination  of,  271 

Spectroscope  (see  Discovery 
of  rubidium  and  caesium), 
202;  spectra  studied  by, 
270-1 

Speculum  Metal  (see  Alloys), 
284 

Spelter,  Table,  281 

Spiegeleisen  (see  Manganese), 
181 

Spirit  Alcohol  (see  Ethyl), 
220 

Spirits  of  Salt,  Table,  281 

Spirits  of  Hartshorn,  Table, 
281 

Sprinklers,  Automatic  (see 
Bismuth),  184 

Stable  Compounds,  explana- 
tion of,  230 


Stalactites  (see  Limestone), 
204 

Stalagmites  (see  Limestone), 
204 

Starch,  elements  contained  in, 
87 

Steel  (see  Iron),  uses  of, 
144-5 ;  preparation  of,  tem- 
pering of,  colors  indicating 
tempering,  149-50;  qualities 
of,  substances  used  for 
cooling,  150-1 ;  effect  of 
various  elements  upon,  Bes- 
semer process  of  manufac- 
ture, 151-2 ;  magnetization 
of,  154;  melting  point  of, 
Thermometer,  276 

Steel  Age,  144 

Stereo  Chemistry,  226;  (see 
also  Table  of  Alloys),  284 

Stone  Age,  tools  and  weapons 
of,  139,  144 

Stromeyer,  Table,  274 

Strontium,  use  in  paints, 
184-5 ;  resemblance  to  cal- 
cium, 185;  calcium  grouped 
with,  203;  discovery  of, 
266-7 ;  Tables,  275-277 ; 
Compounds  of,  184-5;  hy- 
droxide, use  of,  184-5; 
nitrate,  use  of,  185 

Sublimation,    189 

Sugar  of  Lead,  Table,  281 

Sulphates,  of  Aluminium  and 
potassium,  280;  of  cal- 
cium, 125;  ferric  (see  Fer- 
ric Salts),  156;  of  iron  (see 
Copperas,  Table),  280;  of 
Mercury  (see  Mercury,  Ta- 
ble), 281;  of  potassium, 
201 ;  crystallized  s.  of  soda 
(see  Freezing  Mixtures, 
Table),  282;  zinc,  125 

"  Sulphides,"  118 ;  copper, 
iron  s.,  how  produced,  93; 
lead  s.  (see  Galena),  167 

Sulphur,  group  of  elements 
includes,  108;  elements  in 
S.,  group,  116;  extraction 
of,  from  ore,  artificial  pro- 
duction of,  existence  of,  in 


INDEX 


307 


food  products,  in  animal 
bodies,  117;  mercury  com- 
bined with,  properties  of, 
lead  combined  with,  defined 
as  non-metal,  allotropic,  ef- 
fect of  heat  .upon,  117,  118, 
119;  form  of,  soluble  in 
alcohol  and  ether,  120;  use 
of  in  electric  machine,  ef- 
fect of  friction  upon,  six 
different  sorts  of,  insoluble 
form  of,  crystals  of,  120-1 ; 
atomic  weight  of,  uses  of, 
flowers  of,  symbol  for,  col- 
loidal form  of,  amorphous, 
121;  affinity  of  silver  for, 
136,  frequency  of,  in  or- 
ganic compounds,  217;  (see 
also  Tables),  255-7,  277; 
(Thermometer),  276;  Ex- 
plosives), 282;  compounds 
of,  where  found,  117 ;  with 
barium,  use  of,  185;  diox- 
ide, uses  of,  123;  with 
hydrogen,  122 ;  with  potas- 
sium, 182 ;  with  strontium, 
uses  of,  185 

Sulphuric  Acid  (Oil  of  Vit- 
riol), in  extraction  of 
bromine,  112;  formula  for, 
123;  two  classes  of  salts 
formed  by,  important  uses 
of,  importance  of  sulphates 
formed  by,  124-5;  use  of  in 
preparation  nitric  acid, 
189;  use  in  preparation  of 
ethers,  222 ;  decomposition 
of  (see  Electrolysis),  236; 
(see  Tables),  281;  (Explos- 
ives), 283 

Sulphuric  Ether,  282;  (see 
Freezing  Mixtures),  282 

Sun,  271 


Talc  (see  Silicates),  209 
Tannin,    iron    salts   combined 

with,  156 
Tantalum   (see  Table),  275 


Tartar  Emetic  (see  Table 
of  Common  Names),  224, 
281 

Tartaric  Acid  (see  Organic 
Acids),  223 

Tellurides,   116 

Tellurium,  group  of  elements 
includes,  108 ;  sulphur 
group  includes,  116;  atomic 
weight  of,  symbol  for,  de- 
scription of,  discovery  of, 
126;  Table,  275 

Temperatures,  methods  of 
producing  extreme,  232 

Tennant   (see  Table),  275 

Terbium   (see  Table),  275 

Terra  Alba,  use  of  gypsum  in, 
206 

Thallium,  Table,  275 

Theory,  scientific  definition 
of,  56 

Thermit,  temperature  at- 
tained by,  Thermometer, 
276;  (see  also  Alumino- 
thermics),  180 

Thermometer,  276 

Thermopyles  (see  Bismuth), 
184 

Thomson,  265 

Thorium,  Rays  of,  discov- 
ered (see  Schmidt),  271 

Thulium,  Table,  275 

Tin,  atomic  weight  of,  127; 
symbol  for,  characteristics 
of,  foil,  169-70;  use  of,  in 
alloys,  170  (see  also  Table 
of  Alloys),  284;  point  of 
fusion  of,  Thermometer, 
276;  Tables,  275-9;  bi-sul- 
phide  of  (see  Mosaic  Gold, 
Table),  281 

Titanium,  Tables,  275-7 

Travers,  Table,  274-5 

Tri  (prefix)  (see  Chemical 
Nomenclature),  283 

Tungsten  (see  Chromium), 
183;  Table,  275 

Turquoise  ( see  Aluminium 
Phosphate),  178 

Type  Metal  (see  Table  of 
Alloys),  284 


308 


INDEX 


Um  (termination")  (see  Chemi- 
cal Nomenclature),  283 

"Universal    Solvent,"  9 

United  States,  silver  product 
in,  136;  iron  plentiful  in, 
146;  lead  product  in,  167 

Universal  Matter,  Robert 
Boyle's  theory  of,  10 

Uranium  (see  Chromium), 
183 ;  comparative  weight 
of,  183;  rays  of,  discov- 
ered, 271;  proportions  of, 
and  radium  in  pitchblende, 
272;  (see  Table),  275 

Urea,  first  artificial  prepara- 
tion of,  216-7;  (see  Solu- 
tions, discoveries  concern- 
ing), 240 


Valences,  terminology  of,  de- 
fined (footnote),  214 

Valency,  variation  of  ele- 
ments in,  213;  units  of, 
adjectives  of,  256;  theory 
of,  268;  (see  also  Table  of 
Periodic  System),  254-6 

Valentine   (see  Table),  274 

Vandium   (see  Table),  274 

Vapor,  Aqueous,  Volume  of, 
in  normal  air,  Table,  278 

Vauquelin   (see  Table),  274 

Verdigris  (see  Copper  ace- 
tate), 142;  Table,  281 

Vermilion  (see  Pigment  of 
cinnabar),  119;  (see  also 
Two  forms  of  cinnabar), 
171;  Table,  281 

Vitriol,  blue,  green,  white, 
oil  of,  281 ;  uses  of  green 
(see  Ferrous  Salts),  155-6 

Vinegar,  formation  of  verdi- 
gris by  copper  and,  142; 
wine  turns  into  vi  (see  Or- 
ganic Acids),  223 

Volatile  Alkali  (see  Table), 
281 

Volta,  electric  battery  of,  234 


W 

"Washing  Soda"  (see  So- 
dium carbonate),  197;  uses 
of,  198 

Water,  early  beliefs  concern- 
ing, 9;  separation  into 
gases,  12,  15;  chemical 
composition  of  hydrogen 
and  oxygen,  40;  true  na- 
ture of  w.  discovered,  41 ; 
action  of,  chemically  and 
physically,  42,  45;  sub- 
stances deprived  of,  46; 
chemically  an  acid,  101 ; 
dissolution  of  salt  by,  f96; 
affinity  of  calcium  chloride 
for,  206;  application  of 
Avogadro's  Law  to,  250; 
composition  of  discovered, 
264;  experiments  of  Davy 
with,  267;  freezing  point 
of,  boiling  point  of  (Ther- 
mometer), 276;  density  of, 
expansion  of,  rel.  weight 
of,  composition  of  rain, 
Table,  282;  (see  also  Ta- 
ble), 277;  (Freezing  Mix- 
tures), 282 

Watery  Vapor,  as  contained 
in  air,  19 

Wax,  use  of  in  etching,  190 

Waxes,  ethers  used  to  dis- 
solve, 222 

Welsbach   (see  Table),  275 

White  Heat,  degree  of  (Ther- 
mometer), 276 

White  Lead,  processes  for 
preparation  of,  description 
of,  169 

White  Wash  (see  Calcium 
hydroxide),  205 

White  Vitriol,  125 

Wine  (see  Organic  Acids), 
223 

Winkler  (see  Table),  274 

Williams,  Dr.  Henry  Smith, 
demonstration  of,  concern- 
ing atomic  theory,  266 

Wohler,  aluminium  first  ob- 
tained by,  175-6;  urea  ar- 


INDEX 


309 


tificially  prepared  by,  21G-7, 
225,  267,  269 ;  Table,  274 

Wollaston,     Dr.,     demonstra- 
tions of,  265;  Table,  275 

Wood,   burned  by  nitric  acid 
(see  Nitric  Acid),  190 

Wood    Alcohol     (see    Methyl 
Alcohol),  220 

Wrought     Iron     (see    Iron), 
148 

X 

X-Rays   (see  Rontgen  Rays), 

271 
Xenons    (see  Halogens),   109, 

256,  278;    (Tables) 


Yellow  Phosphorus  (see  Phos- 
phorus), 191-2 


Yellow  Pigment  (see  Chromes) , 
183 

Z 

Zero,  Absolute  (Thermome- 
ter), 276 

Zinc  (Spelter),  description 
of,  general  uses  of,  effect 
of  air  upon,  elements  in 
ores  of,  extraction  of,  from 
ores,  use  of,  in  electric 
batteries,  172;  symbol  of, 
173;  (see  Tables),  275,  279, 
281 ;  proportions  of,  in  al- 
loys (see  Table  of  Alloys), 
284;  Chloride  of,  how  pro- 
duced, 93-4,  173;  oxide  of, 
173 ;  sulphate,  125 ;  uses  of, 
173;  (see  White  Vitriol, 
Table),  281 

Zisconium   (see  Table),  275 


THIS  BOOK  IS  DUE  ON  THE  LAST  DATE 
STAMPED  BELOW 


AN  INITIAL  FINE  OF  25  CENTS 

WILL  BE  ASSESSED  FOR  FAILURE  TO  RETURN 
THIS  BOOK  ON  THE  DATE  DUE.  THE  PENALTY 
WILL  INCREASE  TO  SO  CENTS  ON  THE  FOURTH 
DAY  AND  TO  $1.OO  ON  THE  SEVENTH  DAY 
OVERDUE. 


MM 


205100 


